U.S. patent application number 10/782931 was filed with the patent office on 2004-08-26 for composite sheet having elasticity, elastic web made from thermoplastic elastomer, and method and apparatus of manufacturing the same.
This patent application is currently assigned to NIPPON PETROCHEMICALS CO., LTD.. Invention is credited to Kobayashi, Kenichi, Kurihara, Kazuhiko, Yazawa, Hiroshi.
Application Number | 20040166756 10/782931 |
Document ID | / |
Family ID | 27471980 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040166756 |
Kind Code |
A1 |
Kurihara, Kazuhiko ; et
al. |
August 26, 2004 |
Composite sheet having elasticity, elastic web made from
thermoplastic elastomer, and method and apparatus of manufacturing
the same
Abstract
A composite sheet comprises a nonwoven fabric and a rubber
elastic material bonded onto the nonwoven fabric. The nonwoven
fabric has nonelastic fibers aligned in one direction and has
elongation of 100% or higher in a direction perpendicular to the
aligned direction of the nonelastic fibers. The rubber elastic
material is bonded to the nonwoven fabric in a pattern having
orientation perpendicular to the aligned direction of the
nonelastic fibers.
Inventors: |
Kurihara, Kazuhiko; (Tokyo,
JP) ; Yazawa, Hiroshi; (Tokyo, JP) ;
Kobayashi, Kenichi; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
NIPPON PETROCHEMICALS CO.,
LTD.
Tokyo
JP
POLYMER PROCESSING RESEARCH INSTITUTE LTD.
Tokyo
JP
|
Family ID: |
27471980 |
Appl. No.: |
10/782931 |
Filed: |
February 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10782931 |
Feb 23, 2004 |
|
|
|
09572386 |
May 16, 2000 |
|
|
|
Current U.S.
Class: |
442/366 |
Current CPC
Class: |
B29C 55/20 20130101;
Y10T 442/643 20150401; D04H 3/12 20130101; B29C 43/28 20130101;
D04H 3/14 20130101; D04H 1/593 20130101; B29C 55/14 20130101; B29C
55/165 20130101; D04H 3/04 20130101; B29C 55/08 20130101; D04H 1/74
20130101 |
Class at
Publication: |
442/366 |
International
Class: |
B32B 005/02; B32B
027/04; B32B 027/12; D04H 001/74; D04H 003/05 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 1999 |
JP |
11-136176 |
Jun 25, 1999 |
JP |
11-179959 |
Jul 9, 1999 |
JP |
11-196103 |
Sep 8, 1999 |
JP |
11-254104 |
Claims
What is claimed is:
1. A composite sheet comprising: a nonwoven fabric including
nonelastic fibers aligned in one direction and having elongation of
100% or higher in a direction cross to the aligned direction of
said nonelastic fibers; and a rubber elastic material bonded onto
said nonwoven fabric in a pattern having orientation cross to the
aligned direction of said nonelastic fibers.
2. The composite sheet according to claim 1, wherein said rubber
elastic material is in the form of strands of a thermoplastic
elastomer aligned cross to the aligned direction of said nonelastic
fibers.
3. The composite sheet according to claim 2, wherein said strands
of the thermoplastic elastomer are bonded onto said nonwoven fabric
with space between them.
4. The composite sheet according to claim 3, wherein said strands
are aligned substantially in parallel.
5. The composite sheet according to claim 4, wherein said fibers
are aligned longitudinally in said nonwoven fabric and said strands
are aligned transversely in said nonwoven fabric.
6. The composite sheet according to claim 4, wherein said fibers
are aligned transversely in said nonwoven fabric and said strands
are aligned longitudinally in said nonwoven fabric.
7. The composite sheet according to claim 1, wherein said pattern
includes air permeable portions in long shape in a direction cross
to the aligned direction of said nonelastic fibers.
8. The composite sheet according to claim 7, wherein said rubber
elastic material is a web including a thermoplastic elastomer and
including air holes as said air permeable portions.
9. The composite sheet according to claim 8, wherein said web is
bonded onto said nonwoven fabric after said web is held at a
temperature equal to or higher than a flow beginning temperature of
said thermoplastic elastomer to eliminate its contractile force in
a state where said web is elongated cross to the aligned direction
of said nonelastic fibers.
10. The composite sheet according to claim 9, wherein said web is a
film including openings long in a direction cross to the aligned
direction of said nonelastic fibers, as said air holes.
11. The composite sheet according to claim 9, wherein said web is a
nonwoven fabric including thermoplastic elastomer fibers aligned
cross to the aligned direction of said nonelastic fibers.
12. The composite sheet according to claim 7, wherein said rubber
elastic material is formed by heating powder of a thermoplastic
elastomer applied onto said nonwoven fabric in said pattern at a
temperature equal to or higher than a flow beginning temperature of
said thermoplastic elastomer to bring said thermoplastic elastomer
into close contact with said nonwoven fabric.
13. A method of manufacturing a composite sheet comprising the
steps of: composing a nonwoven fabric including nonelastic fibers
aligned in one direction; and bonding a rubber elastic material
onto said nonwoven fabric with orientation cross to the aligned
direction of said nonelastic fibers.
14. The method of manufacturing a composite sheet according to
claim 13, wherein said step of composing the nonwoven fabric
includes aligning said nonelastic fibers in a longitudinal
direction of a nonwoven fabric to be formed; and said step of
bonding the rubber elastic material includes aligning strands of a
thermoplastic elastomer in a width direction of said nonwoven
fabric.
15. The method of manufacturing a composite sheet according to
claim 14, wherein said bonding step includes: forming said nonwoven
fabric into a cylindrical shape; moving said nonwoven fabric formed
into a cylindrical shape in the axis direction of said cylindrical
shape; attaching a plasticized thermoplastic elastomer to an inner
surface of said nonwoven fabric on the move along a circumference
of said cylindrical shape; and move solidifying the plasticized
thermoplastic elastomer attached to said nonwoven fabric to provide
said rubber elastic material.
16. The method of manufacturing a composite sheet according to
claim 15, wherein said step of forming said nonwoven fabric into a
cylindrical shape includes: preparing a forming portion including a
cylinder, said nonwoven fabric being supplied to an inner surface
of said cylinder; and supplying said nonwoven fabric along an inner
surface wall of said cylinder.
17. The method of manufacturing a composite sheet according to
claim 16, wherein said step of attaching a plasticized
thermoplastic elastomer to an inner surface of said nonwoven fabric
formed into a cylindrical shape includes: preparing a rotary
spinning head portion in a central portion of said cylinder, said
rotary spinning head portion being supplied thereinto with said
plasticized thermoplastic elastomer and being provided with a
nozzle opened in its outer peripheral surface; and rotating said
rotary spinning head portion at the same time spinninging said
plasticized thermoplastic elastomer from said nozzle to attach said
thermoplastic elastomer to said nonwoven fabric supplied into said
cylinder and moving therein.
18. The method of manufacturing a composite sheet according to
claim 15, wherein said step of composing the nonwoven fabric
includes aligning said nonelastic fibers in a width direction of a
nonwoven fabric to be formed; and said step of bonding the rubber
elastic material includes aligning strands of a thermoplastic
elastomer in a longitudinal direction of said nonwoven fabric.
19. The method of manufacturing a composite sheet according to
claim 15, further comprising the steps of: forming a web including
a thermoplastic elastomer and including air holes; elongating said
web in one direction; and heating said elongated web at a
temperature equal to or higher than a flow beginning temperature of
said thermoplastic elastomer to eliminate a contractile force of
said web, and wherein said step of bonding the rubber elastic
material includes bonding said web with contractile force
eliminated to said nonwoven fabric such that the aligned direction
of said nonelastic fibers is cross to the elongation direction of
said web.
20. The method of manufacturing a composite sheet according to
claim 19, wherein said step of forming a web includes: preparing a
film including a thermoplastic elastomer; and forming slits which
are to serve as said air holes in said film.
21. The method of manufacturing a composite sheet according to
claim 20, wherein said step of forming said slits includes forming
slits long in the elongation direction of said web.
22. The method of manufacturing a composite sheet according to
claim 15, wherein said step of bonding the rubber elastic material
includes: preparing powder of a thermoplastic elastomer; attaching
said powder to said nonwoven fabric in a pattern having orientation
cross to the aligned direction of said nonelastic fibers and having
air permeable portions; heating said nonwoven fabric with said
powder attached thereto at a temperature equal to or higher than a
flow beginning temperature of said thermoplastic elastomer; and
pressing said nonwoven fabric heated at a temperature equal to or
higher than the flow beginning temperature of said thermoplastic
elastomer to said powder.
23. The method of manufacturing a composite sheet according to
claim 22, wherein said step of attaching said powder to said
nonwoven fabric includes: applying a liquid to said nonwoven fabric
in said pattern; and dispersing said powder on said nonwoven fabric
with said liquid attached thereto.
24. The method of manufacturing a composite sheet according to
claim 15, wherein said step of bonding the rubber elastic material
includes: applying a liquid including a material constituting said
rubber elastic material and including a cross-linking agent added
thereto onto said nonwoven fabric in a pattern having orientation
cross to the aligned direction of said nonelastic fibers and having
air permeable portions; and drying said nonwoven fabric having said
liquid applied thereto.
25. The method of manufacturing a composite sheet according to
claim 24, further comprising the step of performing heat treatment
to said nonwoven fabric having said liquid applied thereto for
promoting reaction of said cross-linking agent.
26. A elastic web comprising one or a plurality of laminated
elongated webs with its contractile force eliminated in an
elongated state by holding one or a plurality of material webs
including a thermoplastic elastomer and having air holes at a
temperature equal to or higher than a flow beginning temperature of
said thermoplastic elastomer in the elongated state.
27. The elastic web according to claim 26, wherein said material
web is a nonwoven fabric including thermoplastic elastomer
fibers.
28. The elastic web according to claim 26, wherein said material
web is a film with holes including a thermoplastic elastomer.
29. The elastic web according to claim 26, wherein said material
web is elongated in one direction and the air holes of said
material web are slits long in the elongation direction.
30. The elastic web according to claim 26, wherein each of said
plurality of material webs is elongated in one direction, the
elongation directions of said material webs being the same or
different from one another, and said plurality of elongated webs
are laminated such that the elongation directions intersect.
31. A method of manufacturing a elastic web comprising the steps
of: forming one or a plurality of material webs including a
thermoplastic elastomer and including air holes; elongating said
material web in at least one direction; and heating said elongated
web at a temperature equal to or higher than a flow beginning
temperature of said thermoplastic elastomer to eliminate a
contractile force of said material web in the elongated state.
32. The method of manufacturing a elastic web according to claim
31, wherein said step of forming a material web includes forming a
nonwoven fabric including thermoplastic elastomer fibers.
33. The method of manufacturing a elastic web according to claim
31, wherein said step of forming a material web includes forming
holes in a film including a thermoplastic elastomer.
34. The method of manufacturing a elastic web according to claim
33, wherein said holes are slits, and said step of elongating said
material web includes elongating said film in a longitudinal
direction of said slits.
35. The method of manufacturing a elastic web according to claim
31, wherein said step of elongating material webs includes
elongating each of said plurality of material webs in one
direction, the elongation directions of said material webs being
the same or different from one another, and the method further
comprising the step of overlaying said plurality of material webs
with their contractile force eliminated such that the elongated
directions intersect.
36. The method of manufacturing a elastic web according to claim
31, wherein said step of elongating a material web includes
elongating said material web at a temperature lower than the flow
beginning temperature of said thermoplastic elastomer.
37. The method of manufacturing a elastic web according to claim
31, further comprising the step of heat-pressing said material web
in a state where said material web is heated at a temperature equal
to or higher than the flow beginning temperature of said
thermoplastic elastomer.
38. An apparatus for manufacturing a composite sheet comprising: a
spinning unit for spinning nonelastic fibers to form a nonwoven
fabric having said fibers aligned in one direction; a stretching
unit for stretching the nonwoven fabric formed by said spinning
unit in the same direction as the aligned direction of said fibers;
and a bonding unit for bonding a rubber elastic material onto the
nonwoven fabric stretched by said stretching unit with orientation
cross to the aligned direction of said fibers.
39. The apparatus for manufacturing a composite sheet according to
claim 38, wherein said spinning unit includes a plurality of
nozzles arranged in a width direction of a nonwoven fabric to be
formed for discharging a material of said fibers in a plasticized
state and carrying means for carrying the fibers discharged from
said nozzle in the discharge direction of said fibers; and said
bonding unit includes a cylindrical portion supplied with said
nonwoven fabric along its inner surface for forming said nonwoven
fabric into a cylindrical shape, a moving mechanism for moving said
nonwoven fabric supplied to said cylindrical portion along the axis
direction of said cylindrical portion, and a rotary spinning head
portion in a central portion of said cylindrical portion, said
rotary spinning head portion being supplied thereinto with a
plasticized material of said rubber elastic material and being
provided with a nozzle opened in its outer peripheral surface.
40. The apparatus for manufacturing a composite sheet according to
claim 38, wherein said spinning unit includes a discharge port for
discharging a material of said fibers in a plasticized state,
dispersing means for dispersing the material of said fibers
discharged from said discharge port in a width direction of a
nonwoven fabric to be formed, and carrying means for carrying said
fibers dispersed from said dispersing means in a longitudinal
direction of a nonwoven fabric to be formed; and said bonding unit
includes a nonwoven fabric carrying means for carrying a nonwoven
fabric formed by said spinning unit and a nozzle for discharging a
material of said rubber elastic material to the nonwoven fabric
carried by said nonwoven fabric carrying means.
41. The apparatus for manufacturing a composite sheet according to
claim 38, further comprising an elastic web forming unit for
forming said rubber elastic material to be bonded to said nonwoven
fabric as a web having air permeable portions.
42. The apparatus for manufacturing a composite sheet according to
claim 41, wherein said elastic web forming unit includes elongating
means for elongating said web in one direction and heating means
for heating said elongated web at a temperature equal to or higher
than a flow beginning temperature of a material of said web to
eliminate a contractile force of said web, and said bonding means
bonds said web to said nonwoven fabric such that the elongation
direction of said web is cross to the aligned direction of the
fibers of said nonwoven fabric.
43. The apparatus for manufacturing a composite sheet according to
claim 41, wherein said elastic web forming unit includes a cutter
for forming slits long in one direction in film made from
thermoplastic elastomer, elongating means for elongating the film
having said slits formed therein in a longitudinal direction of
said slits, and heating means for heating said elongated film at a
temperature equal to or higher than a flow beginning temperature of
said thermoplastic elastomer to eliminate a contractile force of
said film, and said bonding means bonds said film to said nonwoven
fabric such that the elongation direction of said film is cross to
the aligned direction of the fibers of said nonwoven fabric.
44. The apparatus for manufacturing a composite sheet according to
claim 38, wherein said bonding unit includes an attacher for
attaching powder of a thermoplastic elastomer as a material of said
rubber elastic material onto said nonwoven fabric in a pattern
having orientation cross to the aligned direction of said fibers
and having air permeable portions, a heater for heating said
nonwoven fabric with said powder attached thereto by said
attachment unit at a temperature equal to or higher than a flow
beginning temperature of said thermoplastic elastomer, and a
presser for pressing said nonwoven fabric heated by said heating
unit and said powder.
45. The apparatus for manufacturing a composite sheet according to
claim 44, wherein said attachment unit includes an application
roller for applying a liquid to said nonwoven fabric in said
pattern and means for dispersing said powder onto said nonwoven
fabric with said liquid applied thereto.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention:
[0002] The present invention relates to a elastic composite sheet
formed by bonding a nonwoven fabric to an elastic material, more
particularly to a elastic composite sheet preferably utilized for
clothes, medical materials or sanitary materials or the like which
require air permeability or moisture permeability such as elastic
support bandages, supporters, sleeves of clothes, and elastic
portions of diapers, to a method of manufacturing the same and to
an apparatus for manufacturing the same.
[0003] Additionally, the present invention relates not only to a
elastic web which is used as a material web to be bonded to a
nonwoven fabric for the aforementioned composite sheet but also as
a elastic web by itself, to a method of manufacturing the same and
to an apparatus for manufacturing the same.
[0004] 2. Description of the Related Art:
[0005] Various types of proposals have been made for a composite
sheet of a nonwoven fabric and an elastic material (for example,
Japanese Patent Laid-open No.174764/96, Japanese Patent Laid-open
No.132856/97, Japanese Patent Laid-open No.279453/97, and Japanese
Patent Laid-open No.222759/99). These composite sheets, however,
are formed by bonding a previously manufactured elastic product to
a nonwoven fabric in which the elastic material is not arranged in
a direction of elongation, thereby exhibiting unfavorable
elasticity considering the amount of the elastic-material. On the
other hand, in terms of manufacturing the aforementioned composite
sheets, since elastic materials generally have poor processability
, it is difficult to manufacture a composite sheet at low cost with
the conventional methods. For these reasons, there exists a need to
reduce the used amount of the elastic material and to manufacture
aforementioned composite sheets efficiently. Also, since
manufacturing steps of the elastic materials are separated from a
bonding step to the nonwoven fabric, the number of all the steps is
increased, which prevents manufacturing at low cost. Additionally,
since manufacturing steps of the elastic material products are
separated from manufacturing steps of the nonwoven fabric, the
elastic material product is once wound into a roll, and then spread
again and supplied to an apparatus for bonding to the nonwoven
fabric. Since the elastic material product has elasticity, it is
difficult to control the winding and spreading tension. As a
result, this can not be considered as an efficient manufacturing
method.
[0006] In some cases, elasticity is necessary in only one of
longitudinal and transverse directions depending on a application,
and such a composite sheet is desired.
[0007] A conventional composite sheet uses a nonwoven fabric of a
card web or an air layed web which is formed by short fibers, it
has a low surface strength and tends to fall out of short fibers
especially, if the sheet is manufactured by elongating only in one
direction. Such a composite sheet also has poor productivity,
resulting in a higher cost. Additionally, when producing a light
weight sheet, a required strength can not be ensured. Particularly,
with a fiber amount per square meter of 10 g/m.sup.2 or lower,
since a sufficient tension can not be applied, it is very difficult
to manufacture.
[0008] As a prior art in the field, there is a method in which a
spun-bonded nonwoven fabric is slightly embossed and then stretched
longitudinally to shrink in the width before further embossing (see
Japanese Patent Laid-open No.132856/97). In this method, it
requires two embossing steps, and is complicated and has poor
productivity. Since the conditions of embossing are subtle, stable
properties can not be obtained in many cases. Additionally, since
the shrinkage of the nonwoven fabric in the width produces a larger
thickness at both edges, it is difficult to manufacture a product
at uniform thickness resulting in a reduced yield.
[0009] Japanese Patent Laid-open No.279453/97 and Japanese Patent
Laid-open No.279460/97 also disclose prior arts in the field. The
prior arts disclosed in these have a disadvantage similar to the
aforementioned Japanese Patent Laid-open No.132856/97 that it is
difficult to obtain a uniform product and the yield is low because
of inadequate stretching which causes shrinkage in a width These
inventions derive various requirements for exhibiting elasticity
only with a nonwoven fabric. While these inventions use a
stretching factor from 1.4 to 4, the stretching factor defined in
the present invention is assumed to be 2 or lower, considering
shrinkage in the width direction as mentioned above.
[0010] A elastic composite sheets is used as clothes, medical
supplies, sanitary materials, diapers or the like for human bodies
or animals. They need to have an air permeability and moisture
permeability in common for preventing stuffiness. These
applications also require soft texture like a cloth. Thus, bonding
a rubber elastic film directly to the nonwoven fabric can not
eliminate the stuffiness.
[0011] Therefore, a thermoplastic elastomer nonwoven fabric
(Japanese Patent Publication No.55249/86) or a net made from
elastomer (Japanese Patent Publication No.59901/84) has been used,
or strands of elastomer have been used in the aforementioned
applications.
[0012] However, when a elastic web is made of nonwoven fabric, the
random alignment of filaments results in a larger number of the
filaments do not efficiently. function for providing elasticity in
a desired direction. Thus, the filaments in a direction requiring
no elasticity are useless. When a net is used, similarly, a larger
number of components do not function. It is also difficult to
manufacture a web due to the poor processability. Furthermore, a
thick web is too strong and is not suited for applications which
requires soft elasticity.
[0013] On the other hand, the use of the elastomer strands as it is
requires equipment and space for spreading a number of strands.
Also, since the elastomer strands have elasticity, it is difficult
to spread them out at high speed and complicates the
processing.
[0014] Elasticity is often required only in one direction depending
on its application, longitudinally or transversely.
SUMMARY OF THE INVENTION
[0015] It is an object of the present invention to provide a
composite sheet of a nonwoven fabric and an elastomer which has
large elasticity in one direction but has little elasticity in
other directions.
[0016] It is another object of the present invention to provide a
composite sheet which effectively uses a rubber elastic material
and has large elasticity in one direction, as well as has air
permeability.
[0017] It is a further object of the present invention to provide a
elastic web which uses a thermoplastic elastomer of poor
processability but has a small basis weight and elasticity in any
desired direction and is preferably used not only as a web of the
aforementioned composite sheet of the present invention but also as
a web by itself.
[0018] It is a yet further object of the present invention to
provide a method of manufacturing the aforementioned composite
sheet and the elastic web of the present invention.
[0019] The composite sheet of the present invention has a nonwoven
fabric and a rubber elastic material bonded onto the nonwoven
fabric. The nonwoven fabric has nonelastic fibers aligned in one
direction and has elongation of 100% or higher in a direction cross
to the aligned direction of the nonelastic fibers. In other words,
the nonwoven fabric is hardly deformed in the aligned direction
direction of the fibers but is deformable in the direction cross to
the aligned direction of the fibers. The rubber elastic material is
bonded to the nonwoven fabric in a pattern having orientation cross
to the aligned direction of the nonelastic fibers. This results in
a composite sheet which is hardly deformed in the aligned direction
of the fibers but has large elasticity in the direction cross
thereto even with a reduced fiber amount per square meter of the
nonwoven fabric and a reduced amount of the rubber elastic material
used.
[0020] According to a preferred aspect of the composite sheet of
the present invention, the rubber elastic material is in the form
of strands of a thermoplastic elastomer aligned perpendicular to
the aligned direction of the nonelastic fibers. It is preferable to
align the elastomer strands with space between them in order to
reduce the used amount of the elastomer. Full advantage of the
aforementioned elasticity can be taken when a direction with large
elasticity is substantially perpendicular to a direction with
little elasticity. In this case, the aligned direction of the
fibers may be longitudinal or transverse depending on required
elasticity.
[0021] According to another preferred aspect of the present
invention, the aforementioned pattern has air permeable portions in
long shape in a direction perpendicular to the aligned direction of
the nonelastic fibers. With this air permeable portions, air
permeability is not prevented even when the rubber elastic material
is used for expanding and contracting the sheet. In this case, a
web made from thermoplastic elastomer can be used as the
aforementioned rubber elastic material, and the aforementioned air
permeable portions are formed as air holes.
[0022] When the rubber elastic material is a web made from
thermoplastic elastomer, the web may be bonded onto the nonwoven
fabric after the web is held at a temperature equal to or higher
than a flow beginning temperature of the thermoplastic elastomer to
eliminate its contractile force in a state where the web is
elongated perpendicularly to the aligned direction of the
nonelastic fibers. In this case, the air holes of the web may be
fine since the air holes are enlarged with the elongation. Since
the elongation direction of the web is perpendicular to the aligned
direction of the nonelastic fibers, the air holes are also enlarged
in that direction, resulting in improvement in utilization
efficiency of the elastomer in the elasticity direction of the
composite sheet. Also, since the elongation tension of the web is
already lost in a state where the web is bonded to the nonwoven
fabric, the elongation of the web does not affect the elastixity of
the composite sheet. The web may be a film having openings long in
a direction perpendicular to the aligned direction of the
nonelastic fibers as air holes, or may be a nonwoven fabric
including thermoplastic elastomers fibers aligned perpendicularly
to the aligned direction of the nonelastic fibers.
[0023] In another preferred aspect of the composite sheet of the
present invention, the rubber elastic material is formed by heating
powder of a thermoplastic elastomer applied onto the nonwoven
fabric in the pattern at a temperature equal to or higher than a
flow beginning temperature of the thermoplastic elastomer to
integrate the thermoplastic elastomer with the nonwoven fabric.
[0024] A method of manufacturing a composite sheet of the present
invention comprises the a step of composing a nonwoven fabric made
of nonelastic fibers aligned in one direction, and a step of
bonding a rubber elastic material onto the nonwoven fabric with
orientation cross to the aligned direction of the nonelastic
fibers.
[0025] According to a preferred aspect of the method of
manufacturing a composite sheet of the present invention, the
nonwoven fabric composing step includes aligning the nonelastic
fibers in a longitudinal direction of a nonwoven fabric to be
formed, and the bonding step includes aligning strands of a
thermoplastic elastomer in a width direction of the nonwoven
fabric. Alternatively, the nonwoven fabric forming step may include
aligning the nonelastic fibers in a width direction of a nonwoven
fabric to be formed, and the bonding step may include aligning
strands of a thermoplastic elastomer in a longitudinal direction of
the nonwoven fabric. When the strands are aligned in a width
direction of the nonwoven fabric in the bonding step, the bonding
step may include forming the nonwoven fabric into a cylindrical
shape, moving the nonwoven fabric formed into a cylindrical shape
in the axis direction thereof, attaching a plasticized
thermoplastic elastomer to an inner surface of the nonwoven fabric
on the move along a circumference of the cylindrical shape, and
solidifying the plasticized thermoplastic elastomer attached to the
nonwoven fabric to provide the rubber elastic material.
[0026] In another preferred aspect of the method of manufacturing a
composite sheet of the present invention, a web made of
thermoplastic elastomer and having air holes is prepared separately
from a nonwoven fabric made from nonelastic fibers and the web is
bonded onto the nonwoven fabric. Before the bonding to the nonwoven
fabric, the web is elongated in one direction, and in that state,
the web is heated at a temperature equal to or higher than a flow
beginning temperature of the thermoplastic elastomer to eliminate
the contractile force of the web. In the bonding step, the web with
its contractile force eliminated is bonded to the nonwoven fabric
such that the aligned direction of the nonelastic fibers is
perpendicular to the elongation direction of the web.
[0027] In a further preferred aspect of the method of manufacturing
a composite sheet of the present invention, in the bonding step,
powder of a thermoplastic elastomer is first prepared. Next, the
powder is attached to the nonwoven fabric in a pattern having
orientation perpendicular to the aligned direction of the
nonelastic fibers and having air permeable portions. The nonwoven
fabric with the powder attached thereto is heated at a temperature
equal to or higher than the flow beginning temperature of the
thermoplastic elastomer. The heated nonwoven fabric is hot-pressed
with the powder. Thus, the grains of the powder are mutually
adhered and the thermoplastic elastomer is integrated with the
nonwoven fabric.
[0028] According to the method of manufacturing a composite sheet
of the present invention described above, the aforementioned
composite sheet of the present invention is conveniently and
efficiently manufactured.
[0029] A elastic web of the present invention comprises one or a
plurality of laminated elongated webs. The elongated webs have been
eliminated the contractile force in an elongated state by holding
one or a plurality of material webs including a thermoplastic
elastomer and having air holes at a temperature equal to or higher
than a flow beginning temperature of the thermoplastic elastomer in
the elongated state. When a plurality of the elongated webs are
laminated to constitute a elastic web, each of the plurality of
material webs is elongated in one direction. The elongation
directions thereof can be same or different from one another. The
plurality of elongated webs which have been elongated in one
direction to eliminate the contractile force are laminated such
that the elongation directions thereof intersect.
[0030] According to the elastic web of the present invention, the
material web is heated in an elongated state at a temperature equal
to or higher than the flow beginning temperature of the
thermoplastic elastomer to eliminate the contractile force, but the
orientation of the web from the elongation is maintained. Thus,
thermoplastic elastomer can be effectively utilized and the web has
elasticity in a desired direction in accordance with the elongation
direction. Also, the elongation thins the thickness of the web to
result in a smaller basis weight. Additionally, since the material
web has the air holes which are enlarged by the elongation of the
web, the air permeability of the elastic web is not impaired even
with small air holes.
[0031] Such a elastic web can be used by itself, but preferably, it
can be used with connection to another elastic material, for
example a nonwoven fabric, as a rubber elastic material in the
composite sheet in the present invention.
[0032] A method of manufacturing a elastic web of the present
invention comprises the steps of forming one or a plurality of
material webs made of thermoplastic elastomer which have air holes,
elongating the material web in at least one direction and heating
the elongated web at a temperature equal to or higher than a flow
beginning temperature of the thermoplastic elastomer to eliminate
the contractile force of the material web in the elongated state.
When the elastic web is manufactured from a plurality of material
webs, each of the plurality of material webs is elongated in one
direction in the step of elongation, the elongation directions
thereof can be the same or different from one another. After the
step of eliminating the contractile force of the material webs, the
plurality of material webs with the contractile force eliminated
are laminated such that the elongation directions intersect.
[0033] According to the method of manufacturing a elastic web of
the present invention, the aforementioned elastic web of the
present invention is conveniently and efficiently manufactured. The
elongation of the material web is preferably performed at a
temperature lower than the flow beginning temperature of the
thermoplastic elastomer for uniformly elongating the material web.
The method may include the step of heat-pressing the material web
in which the material web is heated at a temperature equal to or
higher than the flow beginning temperature of the thermoplastic
elastomer to obtain a thinner elastic web to provide a flexible
elastic web.
[0034] Additionally, according to one aspect of the present
invention, an apparatus for manufacturing a composite sheet is
provided.
[0035] The apparatus for manufacturing a composite sheet of the
present invention comprises a spinning unit for forming a nonwoven
fabric having nonelastic fibers akigned in one direction, a
stretching unit for stretching the nonwoven fabric formed by the
spinning unit in the aligned direction of the fibers, and a bonding
unit for bonding a rubber elastic material onto the nonwoven fabric
stretched by the stretching unit. The bonding unit is provided for
bonding with orientation perpendicular to the aligned direction of
the fibers forming the nonwoven fabric.
[0036] The spinning unit may align the fibers in a longitudinal
direction of a nonwoven fabric to be formed, or in a transverse
direction. Accordingly, the bonding unit is configured to discharge
the material of the rubber elastic material in the transverse
direction of the nonwoven fabric.
[0037] The apparatus for manufacturing acomposite sheet of the
present invention may include an elastic web forming unit for
forming the rubber elastic material as a web having air permeable
portions. In this case, the nonwoven fabric and the rubber elastic
material are formed in separate steps and then they are bonded by
the bonding unit. When the rubber elastic material is formed as a
web, the web is bonded to the nonwoven fabric in a state where the
web is elongated in one direction and heated at a temperature equal
to or higher than a flow beginning temperature of the web material
to eliminate the contractile force.
[0038] Additionally, the bonding unit of the apparatus for
manufacturing a composite sheet of the present invention may
include an attacher for attaching powder of a thermoplastic
elastomer onto the nonwoven fabric, a heater for heating the
nonwoven fabric with the thermoplastic elastomer powder attached
thereto at a temperature equal to or higher than a flow beginning
temperature of the thermoplastic elastomer, and a presser for
pressing the heated nonwoven fabric and the thermoplastic powder.
In this case, the attacher attaches the thermoplastic elastomer
powder to the nonwoven fabric in a pattern having orientation
perpendicular to the aligned direction of the fibers of the
nonwoven fabric and having air permeable portions.
[0039] It should be noted that, in the present invention, "a
longitudinal direction" of a elasticity direction of a composite
sheet or a web, or a stretching direction of filaments means a
machine direction or feeding direction of a nonwoven fabric or a
web when the nonwoven fabric or web is manufactured, or when the
nonwoven fabric is bonded to an elastomer. On the other hand, "a
transverse direction" means a direction perpendicular to the
longitudinal direction or a width direction of the nonwoven fabric
or web.
[0040] Additionally, "elongation" in the present invention,
includes not only elongation in one direction but also even
elongation in two directions if an elongation factor in one
direction is higher than that in the other direction.
[0041] "Fibers" in the present invention refers to fibers in a
broad sense including both short fibers and continuous filaments.
Long fibers include fibers branching out into some fibers like as a
split web or a burst fiber.
[0042] "Nonelastic fiber" means the fiber not having rubber
elasticity. The rubber elasticity means the nature that a elongated
material contracts in substantially original length by releasing
from elongating force at normal temperature. That is to say,
"nonelastic fiber" means the fiber which keeps substantially
elongated length even if the elongating force is released. However,
it is not necessary that the fiber keeps the elongated length
completely. The nonelastic fiber includes a fiber which contracts
in elasticity 50% or less preferably 20% or less of elongation
[0043] The fibers in the present invention may be typical fibers
made of polymers for synthetic fibers such as polypropylene,
polyamide or polyester, fibers for natural fibers such as cotton or
silk, or fibers for semisynthetic fibers such as rayon or
acetate.
[0044] The nonwoven fabric in the present invention need to have
elongation of at least 100% or higher in one direction. Examples of
such a nonwoven fabric having elongation of 100% or higher include
a nonwoven fabric having fibers aligned in one direction in which
the elongation is 100% or higher in a direction perpendicular to
the aligned direction of the fibers (Japanese Patent Laid-open
No.174764/96, Japanese Patent Laid-open No.222759/99).
[0045] In the present invention, elongation of 100% or higher is
provided in a direction perpendicular to the aligned direction of
the fibers, while elongation is several % to several tens of % with
large elongation stress and thus dimensional stability in the
aligned direction of the fibers is obtained.
[0046] The nonwoven fabric in the present invention employs
nonwoven fabrics made from long fibers such as nonwoven fabrics
obtained by stretching spun bonded nonwoven fabrics or melt blown
nonwoven fabrics, nonwoven fabrics described in detail as a
longitudinally stretched nonwoven fabric or transversely stretched
nonwoven fabric in earlier inventions of the present inventors
(Japanese Patent Publication No.36948/91, Japanese Patent Laid-open
No.204767/98 or the like), nonwoven fabrics having an alignment in
one direction obtained by opening tows, or the like. These long
fiber filaments have no fiber fall out even after elasticity
repeated several hundreds of times and is suited for so-called
lint-free use. The stretched nonwoven fabrics have a high strength
and dimensional stability in the stretching direction and also have
a gloss, and these characteristics from the stretching can be
utilized in clothes or the like.
[0047] While the present invention uses the expression "a nonwoven
fabric stretched in one direction", it includes even a nonwoven
fabric stretched in two directions in which a stretching factor in
one direction is higher than that in the other direction.
[0048] Additionally, nonwoven fabrics having short fibers aligned
in one direction are suited for the nonwoven fabric in the present
invention. The nonwoven fabrics made from short fibers have texture
like cotton with good touch and are preferred for use in which the
fabric is in direct contact with skin. The nonwoven fabrics having
aligned fibers made from short fibers include carded webs or the
like.
[0049] Elongation of at least 100%, preferably 200% is required in
one direction for the nonwoven fabric in the present invention. The
results of experiments show that the nonwoven fabric with
elongation of 100% or higher in one direction provides repeated
elasticity of 200% or higher as a composite sheet of that nonwoven
fabric and an elastomer.
[0050] It is required that a nonwoven fabric made from nonelastic
fibers used in the present invention has the fibers stretched and
aligned substantially in one direction. The primary reason thereof
is that the alignment of the fibers in one direction facilitates
deformation perpendicular to the aligned direction thereof. Since
the nonwoven fabric is hardly deformed in the aligned direction of
the fibers, a composite sheet using such a nonwoven fabric has
dimensional stability and is conveniently used as a product.
Therefore, no particular limitations are imposed on the nonwoven
fabric as long as the fibers are aligned in one direction.
[0051] The nonwoven fabrics having fibers aligned in one direction
includes not only those having fibers aligned completely in one
direction but also those having most fibers aligned in one
direction to provide an alignment substantially in one direction.
While the degree of the alignment is expressed in many ways, it is
often represented with the ratio of a longitudinal strength to a
transverse strength, i.e. a value obtained by dividing the
longitudinal strength by the transverse strength, and the value is
at least three, and preferably 10 or higher. Additionally, even a
nonwoven fabric having fibers aligned and stretched both
longitudinally and transversely can be utilized as a nonwoven
fabric stretched in one direction in the present invention, if a
stretching factor in one direction is higher than that in the other
direction.
[0052] "Elongation" means as the same as "extension ratio" provided
in JIS-L1085. That is, "elongation" represents the elongated length
percentage at break when the 5 cm width of web is pulled in length
direction with 30 cm/min. with gripping at 10 cm interval in the
length direction.
[0053] "Thermoplastic elastomer" means the material which shows the
rubber elasticity at nearly normal temperature although it is
softened and flowed by heating.
[0054] "Strand" includes a comparatively heavy flexible material of
endless or semi-endless as well as a comparatively fine flexible
material of endless or semi-endless usually called a filament. The
size of the filament is about several 100 tex or less, but the
strand can have a size of about several 1000 tex.
[0055] The above and other objects, features and advantages of the
present invention will become apparent from the following
description with reference to the accompanying drawings which
illustrate examples of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] FIG. 1 is a perspective view of a composite sheet according
to a first embodiment of the present invention;
[0057] FIG. 2 is a schematic perspective view of an example of a
spinning apparatus of melt blow scheme preferably used for
manufacturing a nonwoven fabric having filaments aligned
longitudinally;
[0058] FIG. 3 is a schematic diagram of an example of a
longitudinal stretching apparatus for stretching the nonwoven
fabric (web) manufactured by the spinning apparatus shown in FIG. 1
in the direction of the filaments;
[0059] FIG. 4 is a partially cut away side view of an example of a
bonding apparatus used for bonding strands of a thermoplastic
elastomer transversely to one surface of the nonwoven fabric;
[0060] FIG. 5a and FIG. 5b are drawings for explaining a proximity
stretching unit shown in FIG. 2 in detail;
[0061] FIG. 6 is a schematic sectional view of an example of a
spinning apparatus of spun-bonding scheme;
[0062] FIG. 7 is a schematic diagram of another example of the
longitudinal stretching apparatus for the web;
[0063] FIG. 8 is a schematic diagram of a further example of the
longitudinal stretching apparatus for the web;
[0064] FIG. 9a is a diagram showing a spray head, viewed from the
bottom, of a bonding apparatus for bonding an elastomer
transversely to a nonwoven fabric used in a second embodiment of
the present invention;
[0065] FIG. 9b is a side sectional view of the spray head shown in
FIG. 9a;
[0066] FIG. 9c is a sectional view of the spray head shown in FIG.
9a viewed from the front;
[0067] FIG. 10 is a perspective view of a composite sheet according
to a third embodiment of the present invention;
[0068] FIG. 11 is a schematic perspective view of an example of a
transverse stretching apparatus of pulley type preferable for
transversely stretching filaments with no orientation having many
components aligned transversely;
[0069] FIG. 12 is a drawing showing an example of a transverse
stretching apparatus of groove roll type;
[0070] FIG. 13 is a schematic perspective view of an example of a
bonding apparatus for a web;
[0071] FIG. 14 is a perspective view of a composite sheet according
to a fourth embodiment of the present invention;
[0072] FIG. 15 is a flow chart showing an example of a method for
manufacturing the composite sheet shown in FIG. 13;
[0073] FIG. 16 is a schematic diagram of an example of an apparatus
for forming slits in a film;
[0074] FIG. 17 is a front view of a cutter shown in FIG. 16;
[0075] FIG. 18a is a plan view of a net-like film used for the
composite sheet shown in FIG. 13 before elongation;
[0076] FIG. 18b is a plan view of the net-like film used for the
composite sheet shown in FIG. 13;
[0077] FIG. 19 is a schematic side view of another exemplary
apparatus for transversely elongating the web;
[0078] FIG. 20 is a plan view in section of elongation pulleys and
belts of a web takeover portion of a further exemplary apparatus
for transversely elongating the web;
[0079] FIG. 21a is a plan view of another exemplary web having
elasticity in the transverse direction;
[0080] FIG. 21b is a plan view of the web shown in FIG. 21a before
elongation;
[0081] FIG. 22a is a plan view of a further exemplary web having
elasticity in the transverse direction;
[0082] FIG. 22b is a plan view of the web shown in FIG. 22a before
elongation;
[0083] FIG. 23 is a plan view of a composite sheet according to a
fifth embodiment of the present invention;
[0084] FIG. 24 is a flow chart showing an example of a method of
manufacturing the composite sheet shown in FIG. 23;
[0085] FIG. 25a is a plan view of a net-like film used for the
composite sheet shown in FIG. 23 before elongation;
[0086] FIG. 25b is a plan view of the net-like film used for the
composite sheet shown in FIG. 23;
[0087] FIG. 26 is a flow chart showing another exemplary method of
manufacturing the composite sheet shown in FIG. 23;
[0088] FIG. 27 is a diagram showing a configuration of a proximity
stretching apparatus used as a longitudinal elongation and heat
treatment apparatus for the web;
[0089] FIG. 28 is a flow chart showing an example of a method of
manufacturing a composite sheet according to a sixth embodiment of
the present invention in which a nonwoven fabric is used an
elastomer web;
[0090] FIG. 29 is a flow chart showing another exemplary method of
manufacturing a composite sheet according to a sixth embodiment of
the present invention in which a nonwoven fabric is used an
elastomer web;
[0091] FIG. 30 is a partially cut away schematic perspective view
of a position of a composite sheet manufactured with the steps
shown in FIG. 28;
[0092] FIG. 31 is a diagram for explaining a method of bonding
nonwoven fabrics having longitudinally aligned fibers such that the
fibers thereof are orthogonal to each other;
[0093] FIG. 32a to FIG. 32e are diagrams showing various examples
of material webs before elongation used for manufacturing elastic
webs having elasticity in two or more directions according to a
seventh embodiment of the present invention;
[0094] FIG. 33 is a schematic plan view of an example of an
apparatus for elongating a web in biaxial or longitudinal and
transverse directions and performing heat treatment;
[0095] FIG. 34 is a plan view of an exemplary elastic web having
elasticity in at least two or more directions by overlaying a
plurality of webs according to the seventh embodiment of the
present invention;
[0096] FIG. 35 is a plan view of a composite sheet according to an
eight embodiment of the present invention;
[0097] FIG. 36 is a flow chart showing an example of a method of
manufacturing the composite sheet shown in FIG. 35;
[0098] FIG. 37 is a schematic diagram showing an exemplary
apparatus for manufacturing the composite sheet shown in FIG.
35;
[0099] FIG. 38 is a schematic diagram showing another exemplary
apparatus for manufacturing the composite sheet shown in FIG.
35;
[0100] FIG. 39 is a diagram showing a variation of a pattern of a
rubber elastic material in the composite sheet shown in FIG.
35;
[0101] FIG. 40 is a plan view of a composite sheet according to a
ninth embodiment of the present invention;
[0102] FIG. 41a is a schematic side view of an apparatus for
forming strands in vertical direction on a horizontally stretched
nonwoven fabric;
[0103] FIG. 41b is a schematic plane view of FIG. 41a;
[0104] FIG. 42a is a schematic side view of an example of a cross
overlaying machine for overlaying strands on the nonwoven fabric,
and shows the moving of the strands; and
[0105] FIG. 42b shows the moving of the nonwoven fabric in the
cross overlaying machine shown in FIG. 42a.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0106] (First Embodiment)
[0107] Referring to FIG. 1, there is shown composite sheet 501,
serving as a first embodiment of the present invention, in which
strands of thermoplastic elastomer 504 are bonded onto a surface of
nonwoven fabric 502. Nonwoven fabric 502 is formed by aligning
nonelastic filaments 503 substantially in parallel in a machine
direction, i.e. in a longitudinal direction which is a carrying
direction by a conveyor at the manufacture of nonwoven fabric 502
and then stretching them in the longitudinal direction. The strands
of elastomer 504 are bonded onto nonwoven fabric 502 in a
transverse direction substantially perpendicular to the aligned
direction of filaments 503, i.e. in a width direction.
[0108] While nonwoven fabric 502 used in composite sheet 501 is
slightly deformed longitudinally since filaments 503 are aligned
and stretched longitudinally, it can be deformed considerably in
the transverse direction which is substantially perpendicular to
the aligned direction of filaments 503. Specifically, nonwoven
fabric 502 having filaments 503 aligned and stretched in one
direction has a characteristic by itself that it exhibits uniform
and significant elongation without lack in the direction
perpendicular to the aligned direction of filaments 503 but
exhibits little deformation (elongation of approximately several %)
in the aligned direction of filaments 503. The elongation at break
of nonwoven fabric 502 in the direction perpendicular to the
aligned direction of filaments 503 is 100% or higher, preferably
200% or higher, and most preferably 300% or higher. It is difficult
for a nonwoven fabric having no aligned filaments 503 to have
elongation at break of 100% or higher, and it is useless to bond to
a thermoplastic elastomer. The results of studies have ensured
that, with elongation at break of 100% or higher of the nonwoven
fabric, a composite of it and an elastomer provides repeated
elasticity of 200% or higher.
[0109] No particular limitations are imposed on nonwoven fabric 502
as long as filaments 503 are aligned in one direction. It should be
noted that even a nonwoven fabric having filaments 503 aligned and
stretched both longitudinally and transversely can be utilized as a
nonwoven fabric stretched in one direction which is referred to in
the present invention, if a stretching factor in one direction is
higher than that in the other direction to lose a balance between
the longitudinal and transverse directions.
[0110] Composite sheet 501 has a characteristic that the
deformation is slight in the longitudinal direction due to
filaments 503 stretched and aligned longitudinally but the
deformation is significant in the transverse direction
substantially perpendicular to the stretching direction. Also,
since elastomer 504 is bonded to nonwoven fabric 502, the
elasticity of elastomer 504 allows composite sheet 501 to be
expanded transversely. In other words, composite sheet 501 in the
embodiment is a sheet which is hardly elongated longitudinally but
is elastic transversely.
[0111] As described above, the embodiment utilizes elastomer 504
formed as strands in the elasticity direction of composite sheet
501. It is preferable to form elastomer 504 as strands in that an
expensive elastomer can be effectively used with a small amount.
From the viewpoint of reducing the used amount of the elastomer, it
is most preferable to align the strands of elastomer 504 with space
between them. Elastomer 504 generally have unfavorable formability,
and particularly, the thermoplastic elastomer capable of
withstanding repeated elasticity have unfavorable formability.
Thus, it is desirable to employ the simplest method of forming
strands.
[0112] As a thermoplastic elastomer, an elastomer of polyolefin
base, synthetic rubber, polyester base, polyamide base,
polyurethane base or the like is used. Of these materials,
synthetic rubber base or polyurethane base materials in which
styrene and olef in base monomers are copolymerized are preferable
as a thermoplastic elastomer in the present invention due to a high
factor elasticity and a small stress at expanding. Particularly, a
synthetic rubber of SEBS is most preferable.
[0113] As a polymer suitable for filaments 503, a thermoplastic
resin such as polyethylene, polypropylene, polyester, polyamide,
polyvinyl chloride base resin, polyurethane, fluorine contained
resin, and denatured resins thereof can be used. Also, resins to
which wet or dry spinning means is applicable can be used, such as
a polyvinyl alcohol base resin or polyacrylonitrile base resin, and
particularly, polyester and polypropylene are preferable.
[0114] Filaments 503 are long fiber filaments. The long fibers
herein may be substantially long fibers and refer to those with an
average length longer than 100 mm. The diameter of filament 503 is
preferably 30 .mu.m or smaller, and more preferably 25 .mu.m or
smaller since a diameter of 50 .mu.m or larger represents rigidity
and yarn mingling is insufficient. When a nonwoven fabric of
significant strength is intended, the diameter of filament is
preferably 5 .mu.m or larger. The diameter and length of filament
503 are measured with a photomicrograph.
[0115] The method of manufacturing the composite sheet in the
embodiment will be hereinafter described along with the description
of an apparatus configuration shown in FIG. 2 to FIG. 4.
[0116] First, a spinning apparatus is described with reference to
FIG. 2.
[0117] The apparatus shown in FIG. 2 mainly comprises a spinning
unit including melt blow die 1 and conveyor 7, and a stretching
unit including stretching cylinder 11, takeover nip rolls 14a, 14b
or the like.
[0118] Melt blow (MB) die 1 has a number of nozzles 3 at its end in
which molten resin 2 fed from a gear pump (not shown) is pushed out
from nozzle 3 to form a number of filaments 4. In FIG. 2, melt blow
die 1 is shown in sectional view for clearly showing its structure.
Nozzle 3 is provided at its both ends with air chambers 5a, 5b.
Heated air at high pressure heated at a melting point of the resin
or higher is sent to air chambers 5a, 5b and ejected from slits 6a,
6b at the ends of air chambers 5a, 5b. This maintains filaments 4
pushed out from nozzle 3 in a draftable molten state, and the
friction force caused by the ejection of the hot air achieves draft
of filaments 4 to reduce the diameter of filaments 4. The
aforementioned mechanism is similar to that of a spinning apparatus
in a typical MB scheme. The temperature of the heated air at high
pressure is set to be higher than the temperature of spinning of
filaments 4 by 80 degrees or larger, preferably by 120 degrees or
larger, and more preferably by 200 degrees or larger.
[0119] In the method of forming filaments 4 using melt blow die 1,
the temperature of filaments 4 immediately after they are pushed
out from nozzle 3 can be significantly higher than the melting
point of filaments 4 by increasing the temperature of the heated
air. As a result, the molecular orientation of filament 4 can be
suppressed.
[0120] Air chambers 5a, 5b are formed to have different flowing
amounts of air such that the flowing amount from one air chamber 5a
is smaller than that from the other air chamber 5b, thereby
inclining the feeding direction of filament 4 by angle .alpha. with
respect to the pushing-out direction from nozzle 3. Such
inclination of angle .alpha. in the feeding direction of filament 4
in this manner can be realized also by inclining melt blow die 1
itself, or by using both the methods.
[0121] Conveyor 7 is disposed for carrying filaments 4 pushed out
from nozzle 3 below melt blow die 1. Spray nozzles 8a, 8b are
provided between melt blow die 1 and conveyor 7. Spray nozzles 8a,
8b are provided for spraying atomized water from the font side and
back side of filament 4 toward conveyor 7, respectively, which
cools and solidifies filament 4. While a plurality of spray nozzles
8a, 8b are actually provided, only one nozzle 8a and one 8b are
shown in FIG. 2 for avoiding complication. The jet of sprayed
atomized water causes filament 4 to be inclined by angle .beta.
which is larger than .alpha. and to be integrated on conveyor 7 as
web 9.
[0122] Conveyor 7 is disposed with inclination of angle .gamma.
from a horizontal plane such that the takeover direction of
filaments 4 is lower than the arrival position. It should be noted
that a cooling medium ejected from spray nozzles 8a, 8b does not
necessarily include moisture, and cool air may be used. As
described above, the effects of the inclination of conveyor 7 and
the jet of air or atomized water allow filaments 4 in web 9 on
conveyor 7 to be arranged longitudinally.
[0123] In this manner, the spinning of filaments 4 with inclination
to the conveyor surface results in a favorable alignment of
filament 4 on conveyor 7. Effective methods of inclining the
spinning direction with respect to the conveyor surface include
inclining nozzle 3 with respect to conveyor 7, inclining filaments
4 with the help of a fluid, inclining conveyor 7 with respect to
the pushing-out direction of filaments 4, or the like. When it is
difficult to obtain a favorable arrangement with only one of the
aforementioned inclination methods, a plurality of methods may be
performed in combination.
[0124] When filaments 4 are inclined with the help of a fluid, the
fluid is desirably heated when used near nozzle 3. When the fluid
is not used near nozzle 3, filaments 4 need be heated actively near
nozzle 3. This is because the molecular orientation is suppressed
as much as possible when the diameter of filament 4 is reduced with
draft. While the molecular orientation of filaments 4 is suppressed
as much as possible at the spinning step, individual filament 4 is
desirably aligned longitudinally as much as possible.
[0125] As a fluid used for inclining filament 4, a cool fluid,
particularly a fluid containing atomized water is most preferable
near conveyor 7. This is because the rapid cooling of the spun
filaments 4 prevents the effect of heat and the progression of
crystallization. If the effect of heat caused by a heated fluid or
the like remains, filaments 4 on conveyor 7 is subjected to heat
treatment, thereby advancing the crystallization of filament 4 to
reduce a stretching ability at later steps. The stretching ability
is greatly affected by heat especially when filaments 4 are made
from polyester, and also affected in the case of polypropylene. The
water spray in the embodiment produces the rapid cooling effect due
to cooling of molten filaments 4 by water to provide an enhanced
stretching ability such as a higher stretching factor, a higher
strength or the like. Additionally, since the water spray with
spray nozzles 8a, 8b allows web 9 to be stuck to conveyor 7, the
effects of stable spinning and an improved alignment of filaments 4
can be obtained.
[0126] So-called oily agents for spinning stretching, specifically
oily agents capable of providing properties such as an stretching
ability or removal of static electricity may be added to a liquid
sprayed from spray nozzles 8a, 8b. This enables improvement in the
stretching ability of filaments 4, a reduction in the amount of
fuzz, and enhancement of the strength and elongation after
stretching.
[0127] Since cooled web 9 has no self-adhesion, it may be scattered
over conveyor 7 due to an air flow or the like. However, the
scattering is prevented by sucking with negative pressure sucking
nozzle 10 provided linearly on the back side of conveyor 7 in the
width direction of the conveyor.
[0128] The types of conveyor 7 include a conveyor of a drum screen
type which is frequently used for a melt blown nonwoven fabric
other than a conveyor of flat belt type as shown. In the drum
screen type, the inclination refers to that of the direction of
filaments 4 ejected from nozzle 3 from the vertical direction
toward a winding machine. As a material of conveyor 7, various
materials used for manufacturing the nonwoven fabrics can be used
such as metal wires or plastic wires. As a weave for forming its
meshes, various methods used for manufacturing nonwoven fabrics can
be used such as plain weave or diagonal. A particularly effective
weave of a net is a satin weave in which meshes are arranged
longitudinally. This enhances the effect of a longitudinal
alignment of filaments 4 to improve the strength of web 9.
[0129] The sucking of web 9 with negative pressure sucking nozzle
10 also has the effect of removing heat remaining in web 9 in
addition to the stabilization of web 9 which has been unstable due
to the inclination. It is important to perform the negative
pressure sucking in this case linearly in the width direction of
conveyor 7 and with a small width. Specifically, the negative
pressure sucking of web 9 in the melt blow scheme is performed
mainly for enhancing the alignment of filaments 4, and aims to
prevent filaments 4 from being scattered over conveyor 7 and to
remove the heat of filament 4 on conveyor 7 for improving the
stretching ability. Additionally, the negative pressure sucking
removes the moisture attached to web 9, presenting the effect of
reducing the influence of the moisture at the next stretching step.
Since moisture greatly affects the stretching ability in polyester
such that the stretching factor and the web strength after
stretching are reduced, the negative pressure sucking is
preferable.
[0130] Web 9 on conveyor 7 is sandwiched between stretching
cylinder 11 heated at a stretching temperature and retaining rubber
roll 12 on the back side of a loading surface of the conveyor and
moved onto stretching cylinder 11, and then sandwiched between
retaining rubber roll 13 and stretching cylinder 11 for close
contact with stretching cylinder 11. Web 9 in close contact with
stretching cylinder 11 is subjected to proximity stretching in the
longitudinal direction using a speed difference between stretching
cylinder 11 and takeover nip rolls 14a and 14b (14b is a rubber
roll) thereafter, thereby producing longitudinally stretched
nonwoven fabric 15.
[0131] The proximity stretching is a stretching scheme in which a
web is stretched using a difference in surface speeds between two
adjacent rolls with a short stretching distance (a distance from a
starting point to an end point of stretching) being maintained, and
the stretching distance is desirably 100 mm or shorter.
Particularly, when the filaments are not linearly aligned
longitudinally but warped to some extent, it is important to
maintain the stretching distance as short as possible in the
proximity stretching for effective stretching of individual
filaments. The amount of heat required for the proximity stretching
is typically provided by heating a roll for stretching. Heating
with hot wind or infrared rays is used secondarily at a stretching
point. Hot water, steam or the like may also be used.
[0132] As described above, stretching cylinder 11, retaining rubber
roll 13 and takeover nip rolls 14a, 14b constitute a proximity
stretching unit. The proximity stretching unit is now described in
greater detail with reference to FIGS. 5a and 5b.
[0133] Stretching cylinder 11 is heated at a temperature suited for
the stretching of web 9. For example, the temperature is
110.degree. C. when the material of web 9 is polypropylene, while
the temperature is 85.degree. C. when the material is polyester.
Web 9 is in close contact with stretching cylinder 11 by retaining
rubber roll 13, and if the extent of the close contact is
appropriate, the stretching point is straight in the width
direction at point b where web 9 comes away from stretching
cylinder 11, resulting in ideal proximity stretching. If the close
contact is insufficient, the stretching point moves to a point
toward stretching cylinder 11, resulting in unstable stretching. If
the contact is too close, the stretching point varies between b
point and c point, which also leads to unstable stretching. The
extent of the close contact can be changed by heating retaining
rubber roll 13 with an infrared heater or the like, or changing the
adhesion of the surface of stretching cylinder 11, thereby making
it possible to fix the stretching point near b point. These
conditions vary depending on the speed of conveyor 7, the basis
weight of web 9 or the like. In order to fix the stretching point
at b point, hot wind generating machine 31 is effectively used to
blow hot wind having a linear sectional view over b point as shown
in FIG. 5a. Also, as shown in FIG. 5b, infrared line heater 32 for
linearly collecting light with an infrared heater is effectively
used for heating over b line.
[0134] Longitudinally stretched nonwoven fabric 15 obtained as
described above is further stretched longitudinally, for example
with a stretching apparatus as shown in FIG. 3. Stretching steps of
longitudinally stretched nonwoven fabric 15 will be hereinafter
described with reference to FIG. 3. The stretching apparatus shown
in FIG. 3 may be supplied with longitudinally stretched nonwoven
fabric 15 obtained with the spinning apparatus shown in FIG. 2 or
with web 9 before proximity stretching. In FIG. 3, a simple
expression "web" is used as a representative of them.
[0135] Web 41 is introduced into the stretching apparatus with nip
rolls 42a, 42b, preheated by preheat roll 43, and introduced to
stretching roll 45 as web 44. Nip rubber roll 46 is disposed
opposite to stretching roll 45 and web 47 is stretched
longitudinally between stretching roll 45 and stretching roll 48.
The stretching distance is traveling distance PQ of the web defined
by nip point P between stretching roll 45 and nip roll 46 at a
first stage and nip point Q between stretching roll 48 and nip roll
49 at a second stage, and web 47 is stretched between P and Q.
[0136] When multi-stage stretching with this apparatus is required,
stretching is further performed between stretching roll 48 and
stretching roll 51. The stretching distance in this case is
traveling distance QR of web 50 determined by point Q and nit point
R between stretching roll 51 and nip roll 52. When heat treatment
is required after the longitudinal stretching, web 53 may be
subjected to heat treatment with heat treatment roll 54. Web 53 is
taken over as stretched web 56 through nip rolls 55a, 55b.
[0137] As described above, an apparatus having the shortest
possible stretching distance is suited for the longitudinal
stretching of the nonwoven fabric. As shown in FIG. 3, the
provision of nip rolls 46, 49 and 52 respectively for respective
stretching rolls 45, 48 and 51 fixes stretching points to obtain
stable stretching, allowing stretching at a higher factor. If nip
roll 46 or the like is absent, the stretching point not only moves
from P point toward preheat roll 43 to increase the stretching
distance but also moves to cause interrupted stretching. A web
having filaments aligned as longitudinally as possible is suited
for the longitudinal stretching from the aforementioned principle.
This is because a larger number of the filaments are held at both
ends even with a constant stretching distance due to the
longitudinally long filaments, and the strength of the web after
the stretching is increased. In the apparatus shown in FIG. 3, heat
for the stretching is basically provided by the heated rolls, while
hot wind or infrared rays may be used in combination similarly to
that shown in FIG. 5a or FIG. 5b. Additionally, a cover may be put
over traveling distance PQ or QR of the web to heat the inside
thereof with steam. Even when each of webs obtained by the spinning
apparatus shown in FIG. 2 has a small width, they may be arranged
in parallel and stretched using the stretching apparatus shown in
FIG. 3, thereby making it possible to provide a stretched web with
a large width.
[0138] It is generally important to fix the stretching points in
stretching a web. If stretching points are not fixed, the
stretching factor can not be increased since the entire web is not
uniformly stretched and a sufficient web strength can not be
obtained since the stretched web includes portions stretched at
different factors. The width of a longitudinally stretched nonwoven
fabric in finished form ranges from 1 m to 2 m, or larger. When
such a wide stretched nonwoven fabric is manufactured, proximity
stretching is facilitated if spinning is performed using a die of
small width and pre-stretching is performed in the spun web
manufacturing apparatus. The webs after the pre-stretching are
aligned in parallel and subjected to main stretching to obtain a
nonwoven fabric of large width. At this point, since a low
stretching factor in the main stretching leads to slight shrinkage
of the widths of the webs, the pre-stretched webs may be aligned
parallel with only small overlapping portions which are not
obtrusive. Additionally, since the pre-stretched webs have already
been stretched longitudinally, the main stretching may use a
relatively long stretching distance of proximity stretching.
[0139] In the multi-stage stretching, various means used for
typical web stretching may be applied as stretching means at a
second stage or later, other than the proximity stretching, i.e.
various types of stretching schemes such as roll stretching, hot
water stretching, steam stretching, hot plate stretching. The
proximity stretching is not necessarily required because individual
filaments already extend long in a longitudinal direction after a
first stage.
[0140] In the method of manufacturing the longitudinally stretched
nonwoven fabric, a stretching factor depends on types of polymers
of filaments constituting a web, spinning means or aligning means
for webs or the like. However, when any type or means is used, a
stretching factor is selected such that a high degree of
orientation and a high strength of a web can be achieved. The
aforementioned stretching factor is defined by the following
equation using marks provided on a web before stretching at
predetermined intervals in a stretching direction.
stretching factor=(inter-mark length after stretching)/(inter-mark
length before stretching)
[0141] This stretching factor does not necessarily mean the
stretching factor of the filaments as in typical stretching of long
fiber filament yarn.
[0142] The nonwoven fabric thus stretched longitudinally is
subjected to spin of a thermoplastic elastomer in a molten state or
rich dope, i.e. in a plasticized state by an apparatus to bond the
nonwoven fabric to the elastomer. Next, an example of a bonding
apparatus will be described with reference to FIG. 4.
[0143] The apparatus shown in FIG. 4 comprises forming portion 80
for cylindrically forming nonwoven fabric 98 having filaments
aligned and stretched longitudinally, and elastomer spinning
portion 85 for spinning a thermoplastic elastomer toward nonwoven
fabric 98 onto the inner side of nonwoven fabric 98 which has been
formed into cylindrical shape.
[0144] The forming portion means the mechanism to forms a film,
nonwoven fabric, web or the like which has a plane shape into a
tubular shape continuously. The mechanism is used in a forming,
filing and closing machine for manufacturing a bag with a film,
nonwoven fabric, web or the like, and is called a sailor former or
a former because it resembles a sailor color in shape.
[0145] Forming portion 80 comprises guide cylinder 83 with its axis
direction being arranged in a substantially vertical direction, and
guides 81, 82 attached respectively to the top end and bottom end
of guide cylinder 83. Since each of guides 81, 82 may be the same
as that used for forming a packaging film into cylindrical shape in
a forming, filing and closing machine, detailed description thereof
is omitted. Lower guide 81 is provided to open the tubular nonwoven
fabric 98 which is cut at one point along axial direction.
Although, lower guide 81 is the same as upper guide 82 attaching
upside down case of FIG. 4, various mechanism can be used as the
lower guide. For example, a opening machine using a triangle flame
as the lower guide is available. The opening machine is common to
be used for tubular film manufactured by inflation film process.
Paired rollers 95 are disposed below guide cylinder 83 for taking
out composite sheet 99 obtained after passing through forming
portion 80.
[0146] When nonwoven fabric 98 after longitudinal stretching with
the aforementioned stretching apparatus is supplied to forming
portion 80, associated with the operation of paired rollers 95 for
taking out nonwoven fabric 98, nonwoven fabric 98 is formed into
cylindrical shape with upper guide 81 and then fed downward along
the inner wall of guide cylinder 83. Nonwoven fabric 98 is again
spread into flat shape with lower guide 82 and then wound around
winding roller 96 via paired rollers 95.
[0147] Elastomer spinning portion 85 has spinning head 87 provided
rotatably about an axis in a substantially vertical direction.
Spinning head 87 is attached to rotation axis 86 rotatably
supported coaxially with support shaft 94 fixed to frame 93 of the
apparatus on the outer periphery of support shaft 94, and is
disposed inside guide cylinder 83.
[0148] Pulley 89 is attached to the top end of rotation axis 86 and
transfers rotation via belt 90 from a rotation driving source, not
shown, to cause rotation axis 86 to be rotated around support shaft
94. In the present embodiment, spinning head 87 is driven by pulley
drive mechanism to make an overhaul easy. However, it is possible
for the spinning head driving mechanism to constitute more simply
by connecting support shaft 94 to a rotary driving source. Spinning
head 87 is a hollow and cylindrical member which has a top surface
having annular opening 87a, bottom surface being covered, and a
peripheral wall having nozzle 87b through the wall. While the
present embodiment illustrates the spinning head having cylindrical
shape, the shape is not limited to cylindrical shape, if it is
possible to spin the elastomer by centrifugal force. For example,
the spinning head may be shaped into a hollow prism which has
three, four or more faces, or a hollow propeller-like shape which
has two, three or more arms. In every case, the spinning head is
rotated around the center and the elastomer is spun through the
outer wall by centrifugal force. Preferably the shape of the
spinning head should be cylindrical shape, because other shapes
make the spinning by making turbulence around the spinning
head.
[0149] Moreover, if it is undesirable that plasticized elastomer is
exposed to the air, the spinning head may be made airtight. In this
case for example, support shaft 94 may consist of a outer pipe, a
inner pipe and a drive shaft located inside the inner pipe and
connected to the spinning head. The plasticized elastomer is
supplied into the spinning head through a space between the outer
pipe and the inner pipe, and the spinning head is rotated by
rotating the drive shaft.
[0150] A plurality of nozzles 87a may be formed in accordance with
pitches of elastomer strands on the nonwoven fabric 98.
[0151] Disposed above spinning head 87 is supply pipe 88 with its
end (bottom end) being inserted into the spinning head 87 through
opening 87a. Supply pipe 88 is connected to a extruder or a gear
pump (not shown) such that the elastomer is supplied into spinning
head 87 through supply pipe 88 in a molten state or rich dope, i.e.
in a plasticized state. Heaters 91, 92 are respectively disposed
above and below spinning head 87 for heating spinning head 87 to
maintain the temperature of the elastomer in spinning head 87.
[0152] Next, the operation of the bonding apparatus will be
described. As described above, nonwoven fabric 98 in sheet shape is
formed into cylindrical shape with upper guide 81, and fed downward
along the inner wall surface of guide cylinder 83. In other words,
nonwoven fabric 98 formed into cylindrical shape is moved along the
axis direction of guide cylinder 83 along guide cylinder 83.
[0153] At this point, when the elastomer is supplied from supply
pipe 88 to spinning head 87 at the same time spinning head 87 is
rotated, the elastomer supplied to spinning head 87 is spun from
nozzle 87b by centrifugal force. As a result, the elastomer is spun
onto the inner surface of nonwoven fabric 98 formed into
cylindrical shape, then solidified on nonwoven fabric 98, and
bonded to nonwoven fabric 98.
[0154] In this manner, the spinning of the elastomer using
centrifugal force caused by the rotation of spinning head 87 makes
the elastomer attached onto the inner surface of nonwoven fabric 98
along the periphery of guide cylinder 83. Since nonwoven fabric 98
is fed downward in the meantime, the elastomer is attached onto the
inner surface of nonwoven fabric 98 in spiral form.
[0155] Thereafter, nonwoven fabric 98 is spread into flat shape
after passing through lower guide 82. The elastomer is attached
onto nonwoven fabric 98 in a strand form aligned substantially
perpendicular to the aligned direction of the filaments of nonwoven
fabric 98 by appropriately setting the feeding speed of nonwoven
fabric 98 and the rotation speed of spinning head 87. This results
in composite sheet 99 which is hardly stretched in the fiber
direction of the filaments but is stretched in the aligned
direction of the elastomer strands.
[0156] The aforementioned method in which nonwoven fabric 98 is
formed into cylindrical shape and the elastomer is spun to the
inner surface of nonwoven fabric 98 from rotating spinning head 87
is suitable for manufacturing the composite sheet of the present
invention since the elastomer can be easily and rapidly formed in
strand shape. The strands of the elastomer are aligned transversely
in which the composite sheet is expanded, so that even a small
amount of elastomer can efficiently exert its elasticity in the
transverse direction. Additionally, since the composite sheet is
formed by bonding nonwoven fabric 98 to the elastomer, the
elasticity is not deteriorated even with a small fiber amount per
square meter of nonwoven fabric 98, thereby making it possible to
reduce the amount of nonwoven fabric 98.
[0157] In the embodiment shown in FIG. 4, nonwoven fabric 98 passed
through guide 81 is supplied directly to guide cylinder 83.
Generally, in case of forming a web in tubular, a heat sealing
mechanism which seals both sides ends of the web with each other is
provided between guide 81 and guide cylinder 83. However, in the
present invention, the heat sealing mechanism is not necessary,
since the present invention does not purpose to make the nonwoven
fabric tubular shape.
[0158] According to the present invention, it is an ideal that the
width of nonwoven fabric 98 is equal to the internal circumference
length of guide cylinder 83. However, it is difficult to equalize
the width completely, since the side end of nonwoven fabric 98 is
irregular or nonwoven fabric 98 meanders in guide cylinder 83.
Thus, it is preferable to keep of nonwoven fabric 98 wider than the
internal circumference length of guide cylinder 83, because a gap
will be formed between the both sides ends of nonwoven fabric 98 in
guide cylinder 83, if the width of nonwoven fabric is narrower. If
the gap is formed, the elastomer is sprayed directly and adhered on
guide cylinder 83 at the gap. In a result, the moving of nonwoven
fabric is impeded, because the elastomer sprayed on guide cylinder
83 pulls nonwoven fabric 98.
[0159] Additionally, the strand of the elastomer spun on nonwoven
fabric 98 make contracting of nonwoven fabric 98 in the length
direction of the strand, because the strand is adhered to nonwoven
fabric 98 in a state of expanded by centrifugal force and is
released from centrifugal force after the elastomer is attached on.
In short, the strand contracts after attaching onto nonwoven fabric
98. Thus, even if the width of nonwoven fabric 98 is equal to the
internal circumference length of guide cylinder 83, the gap is
formed in the lower portion of guide cylinder 83 by width reduction
of nonwoven fabric 98 as the result of the contracting of the
strand. For the reasons stated above, it is practicable to keep
width of nonwoven fabric 98 wider than the internal circumference
length of guide cylinder 83.
[0160] In this case, preferably nonwoven fabric 98 is fed to guide
cylinder 83 without sealing the overlapped portions of nonwoven
fabric 98 in order not to make a between the both sides ends of
nonwoven fabric 98 even if the width is shortened.
[0161] It is necessary to cut open the composite sheet obtained by
spraying the elastomer to nonwoven fabric 98 in order to return it
from cylindrical shape to plane shape, because the both sides ends
of nonwoven fabric 98 are connected each other with the strand of
the elastomer, even if the both sides ends are not heat sealed. To
open the composite sheet, at least one cutter (not shown) must be
provided to cut the composite sheet along its moving direction. The
composite sheet cut by the cutter is then opened into plane shape
by lower guide 82.
[0162] The composite sheet may be cut into more than one piece by
using a plurality of cutters, when the composite sheet is cut to
open. In this case, lower guide 82 may be supersede by a simpler
mechanism such as some pairs of turn rolls. Cutting the composite
sheet into some pieces has the advantage of simplifying the
mechanism, if the narrower width of the obtained composite sheet is
not a problem.
[0163] As described above, description has been made using the
respective apparatuses shown in FIG. 2 to FIG. 4 for a method of
manufacturing the composite sheet in which the nonwoven fabric has
the filaments aligned and stretched longitudinally on which the
thermoplastic elastomer is aligned in strand shape in the direction
substantially perpendicular to the aligned direction of the
filaments. While the embodiment employs the nonwoven fabric having
the filaments aligned and stretched longitudinally as mentioned
above, the spinning apparatus and stretching apparatus are not
limited to those shown in FIG. 2 and FIG. 3 as long as they can
manufacture such a nonwoven fabric. In the following, a
modification example of the spinning apparatus and the stretching
apparatus is described.
[0164] First, a variation of the spinning apparatus is described
with reference to FIG. 6. While the spinning apparatus shown in
FIG. 2 uses a melt blow die to provide the filaments with draft
tension, the spinning apparatus shown in FIG. 6 employs a
spun-bonding (SB) method in a narrow sense to provide the filament
with draft tension. In FIG. 6, components identical to those in
FIG. 2 are designated with the same reference numerals for
description.
[0165] In the SB spinning, a number of filaments 22 spun from
spun-bonding die 21 having a number of spinning holes are sucked by
ejector 23 with air 24, and then integrated on conveyor 7
accompanied with the accelerated air by a nozzle of ejector 23. As
shown in FIG. 6, heat insulating wall 26 having heater 27 disposed
therein is provided below spun-bonding die 21. With this structure,
heated air 28 heated at a temperature higher than the melting point
of filaments 22 flows along with the feeding of spun filaments 22
to prevent filament 22 from being cooled directly below
nozzles.
[0166] Filaments 22 are cooled by air including atomized water from
spray nozzle 8 immediately before they are fed to ejector 23, and
are introduced into ejector 23 with the cooling being maintained.
If spray nozzle 8 is absent, filaments 22 are mutually fused within
ejector 23. Air 24 may include atomized water in ejector 23 instead
of spray nozzle 8.
[0167] Filaments 22 accelerated at ejector 23 are turned by barrier
wall 29 disposed with inclination to a loading surface of conveyor
7, sucked by negative pressure sucking nozzle 10, and integrated on
inclined conveyor 7 similarly to the example shown in FIG. 2. This
improves the orientation of filaments 22. While FIG. 6 shows
ejector 23 disposed vertically, the flowing direction from ejector
23 itself may be inclined.
[0168] Heat insulating wall 26 directly below the nozzles of
spun-bonding die 21 shown in FIG. 6 is an introduction path of
heated air 28 heated by heater 27 and serves as a heat insulating
cylinder. However, as another method of holding the portion
directly below the nozzles at high temperature, the portion
directly below the nozzles may be directly heated by an infrared
lamp or the like. In any case, characteristically, the portion
directly below the nozzles is maintained at high temperature to
suppress the molecular orientation of filaments 22 even when the
diameter of filament 22 is reduced with draft. Filament 22 has
suppressed molecular orientation to improve the stretching ability
thereafter if the temperature of heated air 28 shown in FIG. 6 is
higher than the spinning temperature (die temperature) of filaments
22 by 80.degree. C. or larger, more preferably by 120.degree. C. or
larger.
[0169] Next, a variation of the stretching apparatus is described
with reference to FIG. 7. In a stretching apparatus shown in FIG.
7, web 61 is preheated by heating cylinder 62. Small diameter roll
63 rotated at a surface speed equal to the surface speed of heating
cylinder 62 is disposed in close contact with cylinder 62. The
stretching of web 61 is performed between small diameter roll 64
and small diameter roll 65. Thereafter, web 61 is subjected to heat
treatment with cylinder 66, cooled by cooling cylinder 67, and
taken over as longitudinally stretched web 69 via nip roll 68. In
such proximity stretching, since the stretching is performed in an
extremely short distance with small diameter rolls 64 and 65,
shrinkage in width is small and stretching points can be fixed.
[0170] Next, another variation of the stretching apparatus is
described with reference to FIG. 8. In the stretching apparatus
shown in FIG. 8, web 114 is introduced to rolls 124, 124' under
heating via turn roll 123 from pinch rolls 122, 122'. The space
between respective rolls 124, 124' is adjusted to be smaller than
the thickness of web 114. Roll 124' in the later stage is rotated
at a rotation speed slower than that of roll 124 at the former
stage. Web 114 is pressed by two rolls 124, 124' at the same time
it is stretched (rolled) longitudinally with a difference in
rotation speeds between respective rolls 124, 124'. Thereafter, web
114 is nipped by pressing roll 125 with heat treatment being
performed by roll 124' at the later stage, and then taken over as
rolled web 126. This rolling scheme is characterized in that even
an original nonwoven fabric having some nonuniform fiber directions
can be stretched at a high factor, and it is possible to provide
absolutely different properties such as a gloss like pearls put on
the entire rolled nonwoven fabric.
[0171] (Second Embodiment)
[0172] A second embodiment is an example for manufacturing a
composite sheet in which a nonwoven fabric has filaments aligned
and stretched longitudinally on which a thermoplastic elastomer is
aligned in strand shape in a direction substantially perpendicular
to the aligned direction of the filaments, similarly to the first
embodiment.
[0173] However, the second embodiment differs from the first
embodiment in a bonding step of the elastomer to the nonwoven
fabric.
[0174] The embodiment will be hereinafter described with reference
to a bonding apparatus shown in FIGS. 9a to 9c.
[0175] In FIGS, 9a to 9c, spray port 108 of a spray head is
provided for discharging a molten liquid of the thermoplastic
elastomer, and air holes 110-1, 110-2, . . . , 110-6 (typically 3
to 8 holes) are provided around spray port 108. Air holes 110-1,
110-2, . . . , 110-6 are provided with slight inclination such that
the air therefrom intersects elastomer 109 discharged from spray
port 108 in a range from several to several tens of centimeters
from spray port 108. This causes elastomer 109 to be rotated in
spiral form.
[0176] Screen mesh 112 is disposed below the spray head for
carrying the nonwoven fabric having the filaments aligned and
stretched longitudinally.
[0177] On the outside of air holes 110-1, 110-2, . . . 110-6, other
two air holes 111, 111' are provided in parallel with the moving
direction of screen mesh 112 such that they spray air in directions
opposite to each other. The air sprayed from air hole 111 collides
with the air sprayed from air hole 111' and then extends in a
direction perpendicular to the carrying direction of the nonwoven
fabric. With the jet of the air, rotating elastomer 109 is directed
perpendicularly to the carrying direction of the nonwoven fabric
and attached to the nonwoven fabric. As a result, a composite sheet
is obtained in which the strands of elastomer 109 are bonded onto
the nonwoven fabric in a pattern with its components mainly aligned
in the width direction of the nonwoven fabric.
[0178] Since one spray port 108 typically sprays the elastomer in a
width ranging from 100 to 300 millimeter, a plurality of spray port
108 may be provided in accordance with the width of the composite
sheet. When it is desired to provide the elastomer at a higher
density without reducing the carrying speed of the nonwoven fabric,
spray heads may be disposed in multi-stage in the carrying
direction of the nonwoven fabric.
[0179] The forming of the nonwoven fabric by means of spinning of
the filaments, and the stretching of the nonwoven fabric formed
therefrom may be performed in a manner similar to that of the first
embodiment using apparatuses similar to those described in the
first embodiment.
[0180] (Third Embodiment)
[0181] In a third embodiment, description will be made for a case
where filaments of a nonwoven fabric and strands of an elastomer
are aligned in opposite directions to those in the aforementioned
first and second embodiments.
[0182] A composite sheet according to the embodiment, as shown in
FIG. 10, is composite sheet 511 in which nonwoven fabric 512 has
filaments 513 stretched and aligned transversely on which elastomer
514 aligned in strand shape in a direction substantially
perpendicular to the aligned direction of filaments 513 is bonded.
Composite sheet 511 shown in FIG. 10 has a characteristics such
that it is hardly elastic transversely but is elastic
longitudinally.
[0183] The manufacture of the composite sheet of the embodiment
also includes spinning steps of manufacturing the nonwoven fabric
having the filaments aligned in substantially one direction,
stretching steps of transversely stretching the nonwoven fabric
manufactured by a spinning apparatus, and a bonding step of bonding
thermoplastic elastomer to the nonwoven fabric stretched
transversely by a stretching apparatus. The spinning steps and the
bonding step of the respective steps can employ the apparatuses
used in the first or second embodiment.
[0184] Specifically, since the nonwoven fabric is formed from the
filaments aligned transversely, it can be manufactured by utilizing
the bonding apparatus (see FIGS. 9a to 9c) used in the second
embodiment to discharge, instead of the elastomer, a polymer which
is to constitute the filaments from spray port 108 of the spray
head. This causes the filaments to be accumulated with its
components mainly aligned transversely over screen mesh 112
disposed below spray port 108, thereby making it possible to obtain
the nonwoven fabric having an alignment primarily in the transverse
direction.
[0185] Similarly to the second embodiment, the number of spray
ports may be increased or reduced in accordance with the width of
the nonwoven fabric to be manufactured, or a plurality of spray
heads may be disposed in accordance with the density of the
filaments.
[0186] When the nonwoven fabric is manufactured using the apparatus
shown in FIGS. 9a to 9c, it is preferable to set the temperature of
air sprayed from respective air holes to be higher than the melting
point of the filaments by several tens of degrees or more in order
to reduce variations in density of the filaments in the
longitudinal direction and to suppress molecular orientation of the
filaments as much as possible. Also, some types of polymers
constituting the filaments may require heating of air sprayed from
only one of two types of the air holes.
[0187] On the other hand, the elastomer is aligned longitudinally,
and the spinning apparatus (see FIG. 2) used in the first and
second embodiments may be utilized. Specifically, while the
transversely stretched nonwoven fabric is carried by conveyor 7,
the thermoplastic elastomer is pushed out from nozzle 3 of melt
blow die 1 to bond the elastomer to the nonwoven fabric.
[0188] In this case, since the elastomer need be solidified after
contact with the nonwoven fabric on conveyor 7, spray nozzles 8a,
8b shown in FIG. 2 are not required. Also, proximity stretching is
not required and thus the stretching unit such as stretching
cylinder 11 is eliminated. It should be noted that in the case of
bonding the elastomer to the nonwoven fabric using the apparatus
shown in FIG. 2, since the density of the elastomer may be lower
than the density of the filaments in manufacturing the nonwoven
fabric, a pitch in arranged nozzles 3 is set as appropriate in
accordance with the density of the elastomer.
[0189] The bonding of the elastomer may employ the apparatus in the
spun-bonding scheme shown in FIG. 6. Additionally, the elastomer
may be aligned longitudinally by means of a number of spray heads
as shown in FIGS. 9a to 9c which are arranged transversely and
rotated by 90 degrees to spread the elastomer longitudinally
(parallel with the traveling direction of a nonwoven fabric) with
the help of air from air holes 111, 111'.
[0190] In this manner, the strands of the elastomer are formed
longitudinally in the process of carrying the nonwoven fabric and
the elastomer is directly bonded to the nonwoven fabric in this
embodiment. More specifically, in the embodiment, in the process of
forming the strands of the elastomer, the elastomer before
solidification reaches the nonwoven fabric, and the elastomer
reaching the nonwoven fabric is solidified and bonded at the same
time on the nonwoven fabric. This enables convenient and efficient
manufacture of the composite sheet having elasticity in the
longitudinal direction. Since the elastomer is aligned in strand
shape longitudinally, even a small amount of elastomer can exert
its elasticity in the longitudinal direction. Additionally, the
amount of the nonwoven fabric can be reduced similarly to the first
embodiment.
[0191] As described above, the spinning of filaments and the
bonding of the elastomer can be performed utilizing the apparatuses
used in the aforementioned respective embodiments, although the
stretching of the nonwoven fabric can not be performed utilizing
the stretching apparatus used in the first and second embodiments
since the aligned direction of the filaments is different from that
in the aforementioned embodiments.
[0192] For this reason, in the present embodiment, the stretching
of the nonwoven fabric in the width direction is performed using,
for example, a transverse stretching apparatus of pulley type as
shown in FIG. 11 or a transverse stretching apparatus of groove
roll type as shown in FIG. 12. Description will be hereinafter made
for the stretching apparatus used for transverse stretching of the
nonwoven fabric in the embodiment.
[0193] Referring to FIG. 11, the transverse stretching apparatus of
pulley type will be first described. Nonwoven fabric 127 comprising
filaments with no orientation is introduced to two stretching
pulleys 129, 129' through turn roll 128. Two pulleys 129, 129' are
arranged to have a track widening gradually toward downstream from
upstream in the moving direction of nonwoven fabric 127, in which
nonwoven fabric 127 is introduced to the narrowest portion in the
track. Endless belts (or ropes) 130, 130' are strained to follow
the track of pulleys 129, 129'. Nonwoven fabric 127 guided by
pulleys 129, 129' are fed with its both edges in the width
direction being pinched by pulleys 129, 129' and endless belts 130,
130', and stretched transversely according to the track created by
pulleys 129, 129'. Nonwoven fabric 127 stretched transversely comes
away from belts 130, 130' at the widest portion in the track of
pulleys 129, 129', and is taken over via turn roll 131. The
gradually widening stretching portion is covered with chamber 132
and heated with hot wind, hot water, infrared rays, or the like. In
the case of hot wind heating, a favorable thermal efficiency
results from heating in which the hot wind passes through nonwoven
fabric 127.
[0194] Next, description will be made for the transverse stretching
apparatus of groove roll type with reference to FIG. 12. In an
example shown in FIG. 12, groove rolls 134, 134' each provided with
alternate peaks and valleys are disposed such that the peaks of one
groove roll 134 match the valleys of the other groove roll 134'.
Nonwoven fabric 135 comprising filaments with no orientation is
inserted between the peaks and valley and stretched transversely by
means of the projections and depressions formed from the peaks and
valleys. Nonwoven fabric 135 after stretching is then subjected to
tentering, and stretching factor may be increased by repeating the
steps on a plurality of times.
[0195] This scheme tends to deteriorate the stretching efficiency
at both edges in the width direction of nonwoven fabric 135.
Countermeasures against that include holding of both edge portions
of nonwoven fabric 135 with rolls at both end portions of groove
rolls 134, 134' which are formed from low elastic material such as
a foaming material or ultra-soft rubber and which have
substantially the same height as that of the peaks of groove rolls
134, 134'. This allows a more favorable stretching efficiency at
both edge portions. As another method, both edge portions of
nonwoven fabric 135 are pulled outward in the width direction by a
thread or thin tape (for example, a stretching tape of polyolefin)
or the like to perform stretching. Alternatively, groove rolls 134,
134' are provided at both end portions with grooves for routing
belts or ropes which hold both edge portions of nonwoven fabric 135
to perform transverse.
[0196] While the first to third embodiments show an example in
which the strands of the elastomer are aligned with space between
them substantially in one direction as described above, the strands
of the elastomer may be aligned such that some of them intersect or
overlap, or the strands of the elastomer may be aligned with no
space between them to provide a web. In this case, the formation of
the elastomer and the bonding to the nonwoven fabric may be
performed in separate steps.
[0197] For example, an elastomer web having orientation in the
transverse direction can be manufactured using the apparatus shown
in FIGS. 9a to 9c. When the formation of the elastomer web and the
bonding to the nonwoven fabric are performed in separate steps, the
elastomer web having orientation in the transverse direction is
heated at a temperature equal to or higher than the softening point
of the elastomer at the same time it is enlarged transversely to
provide an arrangement in the transverse direction. Then, while a
nonwoven fabric having filaments aligned longitudinally is carried,
the elastomer web is placed on the nonwoven fabric, and then the
nonwoven fabric and the elastomer web are bonded under heating
using a calender roll method or an embossing roll method, thereby
obtaining a composite sheet.
[0198] FIG. 13 shows an example of an apparatus for bonding the
elastomer web to the nonwoven fabric. In the apparatus shown in
FIG. 13, nonwoven fabric 141 having filaments aligned
longitudinally and elastomer web 143 having the transverse
alignment are passed through pinch rolls 144, 144' one upon the
other, supplied to heating cylinder 145, and subjected to heat
pressing between heating cylinder 145 and heat pressing roll 146 to
provide composite sheet 147.
[0199] The use of heat is most efficient and inexpensive for
bonding fabric 141 to elastomer web 143. However, for some kinds of
elastomers, both of them may be bonded by interposing an adhesive
third layer such as generally used EVA between nonwoven fabric 141
and elastomer web 143. In this case, one of pinch rolls 144, 144'
is provided with an adhesive bath which supplies an adhesive,
thereby making it possible to bond nonwoven fabric 141 to elastomer
web 143.
[0200] While the example shown in FIG. 13 provides description
assuming that the filaments of nonwoven fabric 141 are aligned
longitudinally and elastomer web 143 is arranged transversely, the
arrangement directions may be reversed.
[0201] (Fourth Embodiment)
[0202] Referring to FIG. 14, there is shown composite sheet 520
according to a fourth embodiment of the present invention in which
net-like film 522 made from thermoplastic elastomer is bonded as a
elastic web to one surface of nonwoven fabric 521. Nonwoven fabric
521 is formed from nonelastic fibers 521a aligned and stretched
substantially longitudinally. Net-like film 522 is provided with a
number of openings 522a long in the transverse direction in meshed
shape, as air holes.
[0203] Since nonwoven fabric 521 used for composite sheet 520 has
fibers 521a aligned and stretched longitudinally, it is deformed
slightly in the longitudinal direction but it can be deformed
significantly in the transverse direction substantially
perpendicular to the aligned direction of fibers 521a. In other
words, it has the characteristic similar to that of the nonwoven
fabric used in the first embodiment.
[0204] Such nonwoven fabric 521 is bonded to net-like film 521 made
from thermoplastic elastomer, thereby obtaining composite sheet 520
which is elastic transversely but is hardly elastic longitudinally
with favorable dimensional stability.
[0205] Since net-like film 522 is provided with a number of
openings 522a, air permeability and moisture permeability are
achieved even when the elastomer is used for providing elasticity
for composite sheet 520. Additionally, the shape of openings 522a
long in the transverse direction enhances the utilization
efficiency of the elastomer in the elasticity direction or
transverse direction, which enables efficient elasticity with a
small amount of the elastomer.
[0206] The thermoplastic elastomer similar to that used in the
first embodiment can be used.
[0207] As fibers 521a, long fiber filaments or short fibers may be
used as long as a nonwoven fabric formed therefrom has a structure
with air permeability and moisture permeability. There is few
fibers to fall out from the nonwoven fabric made of long fiber
filaments even after elasticity repeated several hundreds of times
and is suited for so-called lint-free use. Nonwoven fabrics made
from long fiber filaments include a nonwoven fabric obtained by
stretching a spun-bonded nonwoven fabric or a melt blown nonwoven
fabric, a nonwoven fabric obtained by opening fibers of a tow, or
the like. On the other hand, a nonwoven fabric made from short
fibers has good texture like cotton and is suitable for use in
which the fabric is in direct contact with skin. Nonwoven fabrics
made from short fibers include carded webs or the like.
[0208] While polymers similar to those suitable for the filaments
in the first embodiment may be used as polymers suited for fiber
521a, fibers made from polymers with rubber elasticity such as
polyurethane are eliminated.
[0209] Next, an example of a method of manufacturing composite
sheet 520 will be described with reference to a flow chart in FIG.
15.
[0210] The steps of manufacturing composite sheet 520 are broadly
classified into steps of manufacturing nonwoven fabric 521, steps
of manufacturing an elastomer web (elastic web), and a step of
bonding them.
[0211] In the steps of manufacturing nonwoven fabric 521, first, an
appropriate spinning apparatus is used to obtain a web having
fibers 521a aligned substantially longitudinally (step 1101). Next,
the web is stretched in the aligned direction of fibers 521a,
thereby obtaining a longitudinally stretched nonwoven fabric (step
1102).
[0212] On the other hand, in the steps of manufacturing the
elastomer web, first, slits in the transverse direction are formed
in a film made from elastomer (step 1103). Next, the film having
the slits formed therein is elongated or enlarged transversely
(step 1104). With this step, the film is shrunk longitudinally and
the portions having the slits are expanded transversely to form
openings 522a as shown in FIG. 14. Since the slits are formed
transversely, openings 522a are longer in the transverse direction.
The slits in a staggered arrangement result in an opening pattern
as shown in FIG. 14.
[0213] Next, the film enlarged transversely is heated (heat
treatment) as it is at a temperature equal to or higher than a
temperature at which the material forming the film begins flowing
(step 1105). By holding this state, the contractile force of the
film is lost, and the film maintains the shape shown in FIG. 14
even when the tension applied to the film is removed, thus forming
net-like film 522. In other words, the heating at this step is
performed with tension being applied to the film until the tension
is lost. The heating temperature is preferably higher than the
aforementioned flow beginning temperature by 10 to 20 degrees, more
preferably by 30 to 50 degrees to reduce the time for the
heating.
[0214] The flow beginning temperature is a glass transition
temperature when the hard segment of the elastomer is a
non-crystalline polymer, at which temperature or higher the
elastomer begins flowing. When the hard segment is a crystalline
polymer, its flow beginning temperature is the melting temperature
of the crystal, at which temperature or higher the elastomer begins
flowing. The glass transition temperature and melting temperature
of the thermoplastic polymer are measured with a DSC apparatus in
accordance with JISK 7121. The glass transition temperature and
melting temperature in thermoplastic elastomer form are generally
lower than those in a polymer alone of the hard segment.
[0215] As the heat treatment, constant length heat treatment which
permits no shrinkage is generally. performed, but heat treatment
involving slight shrinkage, i.e. shrinkage heat treatment is also
applicable. The shrinkage preferably ranges from 20 to 30%,
typically in the neighborhood of 10%. Particularly, when the time
or temperature for heat treatment can not be sufficiently ensured,
heat treatment involving slight shrinkage is effective in
eliminating the contractile force.
[0216] Since the width (length in the transverse direction) of a
finished film is derived after the transverse enlargement of the
film at its initial stage, the width of the film at the initial
stage is determined in consideration of the width of the finished
film and the enlargement factor of the film.
[0217] While the enlargement in the transverse direction and the
heating (heat treatment) of the film are herein separately
performed, they may be simultaneously performed. However, the
enlarging step and heating step are preferably separated since the
film formed from the elastomer which is a rubber elastic material
is uniformly elongated by enlargement under heating at room
temperature or low temperature.
[0218] Nonwoven fabric 521 and net-like film 522 obtained as
described above are bonded with their positions in the width
direction being matched (step 1106). Since net-like film 522 is
made from thermoplastic elastomer, simple heating of net-like film
522 causes net-like film 522 to be easily adhered to nonwoven
fabric 521. Therefore, nonwoven fabric 521 and net-like film 522
can be simply bonded at low cost without using an adhesive or the
like.
[0219] In the bonding step, a film before elongation may be
supplied on nonwoven fabric 521, overlaid on nonwoven fabric 521
and heated in a state where the film is elongated to simultaneously
eliminate the contractile force of the film and to bond the film to
nonwoven fabric 521.
[0220] In the following, the aforementioned respective steps will
be described in detail.
[0221] (4-a) Nonwoven Fabric Manufacturing Steps
[0222] Nonwoven fabric 521 can be manufactured typically by
spinning a web using the melt blow method or spun-bonding method
which is a typical spinning method for nonwoven fabrics and then
stretching the web longitudinally. Since the spinning and
stretching can be performed similarly to those in the first
embodiment using a spinning apparatus and a longitudinal stretching
apparatus similar to those shown in the first embodiment, detailed
description thereof is omitted.
[0223] (4-b) Net-Like Film Manufacturing Steps
[0224] Net-like film 522, beginning with an original film made from
thermoplastic elastomer, is manufactured by forming slits in the
original film, elongating it transversely, and heating it to
eliminate the contractile force, as described above. As an original
film, general film are used, for example, those formed with a T die
method, those formed by cutting and opening a tubular film, or the
like.
[0225] First, the slits in the original film can be formed using,
for example, an apparatus shown in FIG. 16. In FIG. 16, film 523
serving as an original film is guided on rotation roller 202 after
passing between nip rollers 201, 201' at room temperature or after
preheating. Rotation roller 202 has cutters 203 fixed radially on
the peripheral surface as shown in FIG. 17, for example. Each of
cutters 203 includes triangular edges 203a arranged in a line and
having cutting edges on their oblique sides. In adjacent cutters
203, triangular edges 203a are arranged such that the positions of
triangular edges 203a of the respective cutters 203 are shifted by
a half pitch in arranged triangular edges 203a.
[0226] The surface speed of rotation roller 202 is higher than the
supply speed of film 523 by nip rollers 201, 201' and cutter 203
cuts film 523 under tension. This allows slits 523a in the
transverse direction to be formed in film 523 in a staggered
pattern as shown in FIG. 18a. Film 523 having slits 523a formed
therein after passing through rotation roller 202 is received by
nip rollers 204, 204' and fed to the next step. It should be noted
that the receiving speed of film 523 by nip rollers 204, 204' is
higher than the peripheral peed of the cutting edges of cutter 203.
This facilitates taking the cutting edges of cutter 203 out of film
523.
[0227] After slits 523a are formed in film 523 as described above,
film 523 is enlarged transversely.
[0228] The transverse enlargement of film 523 is performed using,
for example, the transverse stretching apparatus of pulley type as
shown in FIG. 11, and the width of the film is increased as
follows.
[0229] First, film 523 shown in FIG. 18a is supplied to the
apparatus. The atmosphere in chamber 132 is heated at a temperature
equal to or higher than the flow beginning temperature of the
material of film 523, and the contractile force of film 523 is lost
before film 523 comes away from belts 130, 130'. As a result, film
523 maintains an extended width even after it passes through turn
roll 131 and is taken over, providing net-like film 522 having
openings 522a formed in a mesh pattern as shown in FIG. 18b.
[0230] While description has been made for an example in which the
slits are formed in the original film using the cutter, the
formation of the slits is not limited thereto. The slits may be
formed by irradiating a film with laser beam, infrared rays, or
ultraviolet rays as disclosed in Japanese Patent Laid-open
No.228669/93.
[0231] (4-c) Bonding Step
[0232] For bonding the longitudinally stretched nonwoven fabric to
the net-like film, a calender roll method, an embossing roll method
or the like may be used. Preferably, the longitudinally stretched
nonwoven fabric and net-like film 522 can be bonded by using the
apparatus shown in FIG. 13 to supply net-like film 522 instead of
web 143 of the elastomer.
[0233] In the bonding of nonwoven fabric 521 to net-like film 522,
ultrasound bonding, high frequency bonding, physical bonding
methods such as needle punch, water jet or the like may be used in
addition to the aforementioned methods.
[0234] As described above, the elastomer web and the nonwoven
fabric made from nonelastic fibers are bonded in a state where the
contractile force of the web is eliminated with the elongation and
heating of the thermoplastic elastomer web. Such elongation of the
elastomer web extends the openings in the elastomer web to obtain
the composite sheet having sufficient air permeability and moisture
permeability. The elongation factor of the elastomer web is
typically two, and preferably three or more.
[0235] Additionally, the elongation of the elastomer web reduces
the thickness of the elastomer web and thins the strands
constituting the net to provide increased flexibility, thereby
obtaining the elastic composite sheet which is particularly
preferable for use in clothes or the like. The elongation means
that the original elastomer web may be thick corresponding to the
elongation factor. While it is difficult to manufacture a thin web
at uniform thickness using the thermoplastic elastomer, the
elongation of the web reduces the thickness thereof and thus the
manufacture of the original elastomer web is facilitated.
[0236] In the present embodiment, the elastomer web is elongated
transversely, which enables the manufacture of a product of large
width from an original web of small width. Therefore, the
transverse elongation of the elastomer web reduces cost for
equipment and is preferable for manufacturing a large-width web
using the thermoplastic elastomer of unfavorable formability.
[0237] While the present embodiment illustrates composite sheet 520
in which nonwoven fabric 521 is bonded to net-like film 522,
net-like film 522 forming composite sheet 520 can be used by itself
as a elastic web. When net-like film 522 is used as a elastic web,
net-like film 522 is a film having elasticity primarily in the
transverse direction. The elastic range as a rubber elastic
material in the longitudinal direction is smaller than that in the
transverse direction even when the stress is applied thereto, in
which the elasticity is small only with openings 522a being
widened.
[0238] Since net-like film 522 is formed by transversely elongating
film 523 as described above, a elastic web of large width can be
obtained. In other words, a product of large width can be formed
from an original web of small width so that the cost for equipment
is lower and it is preferable for processing of the thermoplastic
elastomer of unfavorable formability. Additionally, since the film
is elongated to obtain the elastic web, the resulting elastic web
is thinner and flexible in proportion to the elongation factor. As
a result, it has good texture and can be preferably utilized for
use in clothes or the like.
[0239] The elongation direction of the film is determined by the
elongation direction intended by the elastic web, that is, the
transverse direction in the embodiment. A elastic web intending to
expand and contract in the longitudinal direction as later
described is elongated longitudinally, while a elastic web
intending expand and contract both in longitudinal and transverse
directions is elongated both longitudinally and transversely.
[0240] The elongation of the film means that an original film may
be thick according to the elongation factor. While it is difficult
to manufacture a thin original web at uniform thickness using the
thermoplastic elastomer, such a thick original web permitted
facilitates the manufacture of the original web. The elongation
factor is preferably two or more, more preferably three or
more.
[0241] Since the thermoplastic elastomer is susceptible to plastic
deformation in a heated state, heat pressing in a heated state
after heat treatment can flatten the web. Therefore, the web
thinned by the elongation can be further thinned by this heat
pressing. The heat pressing allows the thickness of the web to be
reduced to two-third, preferably one-half or lower. The web becomes
more flexible with soft touch and pliable feeling from the
flattening with the heat pressing. The heat pressing is also
effective in removing the contractile force from the
elongation.
[0242] While the embodiment illustrates the film elongated
transversely and the apparatus shown in FIG. 11 as an example of an
apparatus used therefor, other examples of apparatuses for
transversely elongating the film will be hereinafter described with
reference to FIG. 19 and FIG. 20.
[0243] An apparatus shown in FIG. 19 includes turn pulley 325
movable, for example by replacing a belt or adjusting the position
of a pulley (not shown) for adjusting tension so as to allow
adjustment of a position where belt 322 or film 523 comes away from
elongation pulley 321. In an elongation apparatus of pulley type,
the disposal of elongation pulley 321 as shown also in FIG. 11
defines elongating portion A where the interval between elongation
pulleys 321 is gradually increased, parallel portion B where the
interval between elongation pulleys 321 is substantially constant,
and narrowing portion C where the interval between elongation
pulleys 321 is tapered. In the elongation apparatus shown in FIG.
19, turn pulley 325 is provided movably between parallel portion B
and tapered portion C. Therefore, turn pulley 325 located at
parallel portion B causes film 523 to be elongated similarly to
that described in FIG. 11, while turn pulley 325 located at
narrowing portion C as shown two-dot chain lines causes film 523 to
be slightly narrowed and taken over after elongation up to its
maximum width.
[0244] An elongation apparatus shown in FIG. 20 has metal roll 336
and rubber roll 337 for nipping film 523 disposed near a position
where belts 332, 332' or film 523 comes away from elongation
pulleys 331, 331'. Such disposal of metal roll 336 and rubber roll
337 allows film 523 with no restoring power due to heating to be
pressed in a heated state, thereby obtaining a thinner elastic
web.
[0245] While the apparatuses shown in FIGS. 11, 19 and 20 are
elongation apparatuses of pulley type, the transverse elongation of
the web is not limited to the pulley type, and transverse
elongation apparatuses such as a tentering scheme can be used.
[0246] While description has been made for typical examples of the
transversely elastic web which constitutes the composite sheet
having great elasticity in the transverse direction or which has
elasticity by itself in the transverse direction, along with the
method for manufacturing the same, the shape of the air holes
(openings) in the transversely elastic web is not limited to that
shown in FIG. 14.
[0247] When the transversely elastic web is used in the composite
sheet, it is preferable that the used amount of the elastomer in a
direction perpendicular to the elastic direction of the composite
sheet is smaller than that in the elastic direction from the
viewpoint of the utilization efficiency of the elastomer. Several
preferable patterns of openings will be hereinafter
illustrated.
[0248] Shown in FIG. 21a is an example of ladder-like film 531
having an opening pattern in ladder shape. Openings 531a have
lengths which range substantially across the transverse direction
of ladder-like film 531 in which openings 531a are arranged
longitudinally in ladder-like film 531. Such ladder-like film 531
may be manufactured, as shown in FIG. 21b, by forming slits 530a
ranging substantially across the width direction of film 530
serving as an original film at intervals in the longitudinal
direction, elongating film 530 transversely, and heating film 530
at a temperature equal to or higher than the flow beginning
temperature of the thermoplastic elastomer to remove the
contractile force.
[0249] Shown in FIG. 22a is an example of branch-like film 541
having an opening pattern in which trunk portions 541b and branch
portions 541c with different thickness intersect. Branch-like film
541 comprises trunk portions 541b substantially parallel with the
transverse direction and branch portions 541c which are thinner
than trunk portions 541b and obliquely intersect trunk portions
541b. These trunk portions 541b and branch portions 541 surround
and form openings 541a. Such branch-like film 541 may be
manufactured, as shown in FIG. 22b, by forming slits 540a arranged
in stair shape in the transverse direction in film 540 serving as
an original film, transversely elongating film 540, and heating
film 540 at a temperature equal to or higher than the flow
beginning temperature of the thermoplastic elastomer to remove the
contractile force.
[0250] (Fifth Embodiment)
[0251] Referring to FIG. 23, there is shown composite sheet 550 in
which net-like film 552 made from thermoplastic elastomer provided
with a number of openings 552a long in the longitudinal direction
is bonded as a elastic web to one surface of nonwoven fabric 551
including fibers 551a aligned and stretched substantially
transversely.
[0252] Composite sheet 550 of a fifth embodiment has nonwoven
fabric 551 and net-like film 552 opposite to those in the fourth
embodiment in terms of longitudinal and transverse directions.
Therefore, its characteristics are also opposite to those of the
composite sheet described in the fourth embodiment in terms of
longitudinal and transverse directions. Specifically, composite
sheet 550 of the embodiment is elastic longitudinally but is hardly
expanded in the transverse direction with favorable dimensional
stability. Other characteristics such as air permeability (moisture
permeability), high utilization efficiency of the elastomer and the
like are similar to those in the fourth embodiment. The same
materials constituting nonwoven fabric 551 and elastomers as those
in the fourth embodiment can be used.
[0253] Next, an example of a method of manufacturing composite
sheet 550 in the embodiment will be described with reference to a
flow chart in FIG. 24.
[0254] In the embodiment, similarly to the fourth embodiment, steps
of manufacturing composite sheet 550 are broadly classified into
steps of manufacturing nonwoven fabric 551, steps of manufacturing
the elastomer web, and a step of bonding them.
[0255] In the steps of manufacturing nonwoven fabric 551, first, an
appropriate spinning apparatus is used to obtain a web having
fibers aligned substantially transversely (step 1111). Next, the
web is stretched in the aligned direction of the fibers (step 1112)
to obtain transversely stretched nonwoven fabric 551.
[0256] On the other hand, in the steps of manufacturing the
elastomer web, first, slits long in the longitudinal direction are
formed in a film made from elastomer (step 1113). Next, the film
having the slits formed therein is elongated longitudinally and
heated at a temperature equal to or higher than the flow beginning
temperature for the material of the film (step 1114). This removes
the contractile force of the film. Next, the width of the film
having the slits formed therein is increased (step 1115). At this
point, the film is heated at a temperature equal to or higher than
the flow beginning temperature of the material. This removes the
contractile force of the film, thereby obtaining net-like film 552
provided with openings 552a long in the longitudinal direction as
shown in FIG. 23.
[0257] Nonwoven fabric 551 and net-like film 552 thus obtained are
bonded with their positions in the width direction being matched
(step 1116) to provide composite sheet 550.
[0258] In the following, the aforementioned respective steps will
be described in detail.
[0259] (5-a) Nonwoven Fabric Manufacturing Steps.
[0260] Methods of manufacturing the nonwoven fabric include those,
for example, disclosed in Japanese Patent Publication No.36948/91,
Japanese Patent Laid-open No.6126/95, Japanese Patent No.2612203,
Domestic Republication of PCT International Publication for Patent
Application WO9617121, Japanese Patent Laid-open No.204764/98,
Japanese Patent Laid-open No.222759/99, or the like.
[0261] Since the embodiment employs the nonwoven fabric having the
fibers aligned and stretched substantially transversely, an
apparatus different from that in the fourth embodiment is used for
manufacturing the nonwoven fabric. An example thereof is the
apparatus shown in FIGS. 9a to 9c. With the apparatus, a molten
liquid of a polymer which is to constitute a nonwoven fabric is
discharged from spray port 108 to accumulate fibers on screen mesh
112 with its components mainly arranged transversely, thereby
obtaining the nonwoven fabric with an alignment primarily in the
transverse direction.
[0262] The nonwoven fabric obtained is stretched transversely to
provide the transversely stretched nonwoven fabric. The apparatus
shown in FIG. 11 is utilized as it is for the transverse stretching
of the nonwoven fabric.
[0263] (5-b) Net-Like Film Manufacturing Steps
[0264] Net-like film 522 used in the embodiment, beginning with a
film made from thermoplastic elastomer, is manufactured by forming
flits in the film, elongating it longitudinally, and increasing its
width, as described above.
[0265] First, the slits in the longitudinal direction are formed in
the film. The formation of the slits can be performed by passing
the film over a rotation roller provided with cutters on its
peripheral surface, similarly to the fourth embodiment. Since the
slits long in the longitudinal direction are formed in the
embodiment, the cutters are attached in a direction perpendicular
to that of the cutters used in the second embodiment. This result
in film 553 having slits 553 in the longitudinal direction in a
staggered pattern.
[0266] Next, the film is enlarged longitudinally, which may be
performed using apparatus similar to that used in the longitudinal
stretching of the nonwoven fabric in the fourth embodiment or
general longitudinal stretching apparatuses. In this case, the
enlargement of the film in the longitudinal direction reduces the
width of the film in accordance with the enlargement factor to
cause the slits to be opened correspondingly, thus providing a
net-like film. At this point, the film is heated at a temperature
equal to or higher than the flow beginning temperature to remove
the contractile force.
[0267] Next, the width of the film having the slits formed therein
is increased. At this step, the same apparatus as that used for
increasing the width of the film in the fourth embodiment, i.e. the
apparatus shown in FIG. 11 can be used to increase the width of the
film. At this point, the film is heated at a temperature equal to
or higher than the flow beginning temperature to remove the
contractile force, thereby obtaining net-like film 552 having
openings 552a long in the longitudinal direction as shown in FIG.
25b. It should be noted that the width-increasing factor at this
point is smaller than the factor of the enlargement in the
longitudinal direction. In other words, the film is elongated
relatively in the longitudinal direction.
[0268] While description has been made for an example in which the
slits long in the longitudinal direction are formed in the film,
and the film is enlarged longitudinally and then the width thereof
is increased, the net-like film may be formed by enlarging the film
first longitudinally (step 1113'), forming the longitudinal slits
(step 1114'), and then transversely increasing the width of the
film having the slits formed therein (step 1115') as shown in FIG.
26.
[0269] While the elongation and heat treatment of the film may be
performed simultaneously, it is preferable to separate the
elongation step from the heat treatment step and to perform the
elongation of the film at a temperature lower than the flow
beginning temperature of the thermoplastic elastomer in
consideration of the uniform elongation of the film, similarly to
the fourth embodiment. Additionally, the film after heat treatment
may be subjected to heat pressing in a heated state in order to
obtain a thinner film (web).
[0270] A roll stretching method used for general stretching of
films or nonwoven fabrics can be used for the longitudinal
elongation of the film. In the roll stretching, proximity
stretching means having an extremely short stretching distance for
the web width is most preferable for the longitudinal elongation in
the present invention because the elongation causes no reduction in
width of the web to allow the manufacture of a large-width web and
uniform elongation is provided and because it can manufacture a
thinner web at the same elongation factor as compared with other
stretching methods. Also, the proximity stretching means is compact
in size. Proximity stretching means disclosed in Japanese Patent
Publication No.36948/91 or Japanese Patent Laid-open No.204767/98
is particularly preferable, both of which are earlier inventions by
the present inventors.
[0271] Next, description will be made for an apparatus for
elongating the film longitudinally and performing heat treatment
with reference to FIG. 27. In FIG. 27, film 553 having slits 553a
(see FIG. 25a) formed therein is introduced to elongation cylinder
301 via turn roll 305. Elongation cylinder 301 may be heated, but
usually it is used at room temperature.
[0272] Heat treatment cylinder 304 is disposed with space provided
from elongation cylinder 301 on the downstream side of elongation
cylinder 301 in the moving direction of film 553. Heat treatment
cylinder 304 is provided for heating film 553 at a temperature
equal to or higher than the flow beginning temperature, and is
rotated at a peripheral surface speed higher than the peripheral
surface speed of elongation cylinder 301. This causes film 553 to
be elongated at a factor corresponding to the ratio of the
peripheral surface speeds of both cylinders 301, 304, and in that
state, the contractile force is eliminated. Nip rolls 302, 303 made
from rubber are disposed respectively at a position where film 553
comes away from elongation cylinder 301 and at a position where
film 553 is received by heat treatment cylinder 304, thereby
stabilizing the distance between elongation points in film 553.
[0273] Film 553 with no contractile force after heat treatment by
heat treatment cylinder 304 is pressed between heat treatment
cylinder 304 press roll 306 and is taken over as a elastic web.
[0274] (5-c) Bonding Step
[0275] The nonwoven fabric having the fibers aligned and stretched
transversely can be bonded to the net-like film having the
longitudinally long openings long similarly to the fourth
embodiment.
[0276] (Sixth Embodiment)
[0277] While the aforementioned fourth and fifth embodiments show
the example in which the film having openings is used as an
elastomer web, the present invention is not limited thereto, and a
nonwoven fabric made from thermoplastic elastomer can be used.
[0278] FIG. 28 and FIG. 29 show an example of steps of
manufacturing a composite sheet when a thermoplastic elastomer
nonwoven fabric is used as an elastomer web.
[0279] In the example shown in FIG. 28, a fiber spinning step (step
1121) and a longitudinal stretching step (step 1122) in steps of
manufacturing an nonelastic nonwoven fabric are the same as those
in the fourth embodiment. On the other hand, in steps of
manufacturing an elastomer nonwoven fabric, a nonwoven fabric
having elastomer fibers aligned transversely is first formed (step
1123), it is enlarged transversely (step 1124), and heated at a
temperature equal to or higher than the flow beginning temperature
of the elastomer (step 1125). Next, the nonelastic nonwoven fabric
and the elastomer nonwoven fabric are bonded (step 1126) to
manufacture a composite sheet.
[0280] FIG. 30 shows a composite sheet obtained in this manner.
Composite sheet 560 shown in FIG. 30 comprises nonelastic nonwoven
fabric 561 having nonelastic fibers aligned substantially
longitudinally and elastomer nonwoven fabric 562 having elastomer
fibers aligned substantially transversely.
[0281] Shown in FIG. 29 is an example for manufacturing a composite
sheet which has arrangements of an nonelastic nonwoven fabric and
an elastomer nonwoven fabric opposite to those shown in FIG. 30. In
the example shown in FIG. 29, a fiber spinning step (step 1131) and
a transverse stretching step (step 1132) in steps of manufacturing
the nonelastic nonwoven fabric are the same as those in the fifth
embodiment. On the other hand, in steps of manufacturing the
elastomer nonwoven fabric, a nonwoven fabric having elastomer
fibers aligned longitudinally is first formed (step 1133), it is
enlarged in the longitudinal direction (step 1134), and heated at a
temperature equal to or higher than the flow beginning temperature
of the elastomer (step 1135). Next, the nonelastic nonwoven fabric
and the elastomer nonwoven fabric are bonded (step 1136) to
manufacture a composite sheet.
[0282] For the elastomer nonwoven fabric, nonwoven fabrics
manufactured with a general melt blow method or spun-bonding method
(Japanese Patent Laid-open No.55249/86) can be utilized, or the
spinning method in an earlier invention by the present inventors
(Japanese Patent Laid-open No.242960/90) can be utilized, but the
present invention is not limited thereto. The elongation of the
elastomer nonwoven fabric and the bonding of the nonelastic
nonwoven fabric to the elastomer nonwoven fabric can be performed
using the means for bonding the nonwoven fabric to the film
described in the fourth or fifth embodiment.
[0283] When the elastomer web is made from nonwoven fabric,
openings for air permeability or the like are fine since they are
formed of gaps between fibers in the elastomer. However, even the
fine openings does not impair air permeability or moisture
permeability because the openings are widened at the elongation
step thereafter. The aligned direction of the fibers in the
elastomer when the elastomer web is made from nonwoven fabric is
preferably perpendicular to the aligned direction of the nonelastic
fibers in the nonwoven fabric to be bonded thereto from the
viewpoint of the utilization efficiency of the elastomer in the
elasticity direction of the composite sheet in consideration of the
shapes of the openings after widening at the elongation step. In
other words, at the elongation step of the elastomer nonwoven
fabric, it is preferable to elongate the elastomer web in the
aligned direction of the fibers in the elastomer. This allows the
openings in the nonwoven fabric made from elastomer fibers to be
easily formed into long shape in one direction. Slits may also be
formed to add opening portions in the elastomer nonwoven fabric
similarly to the films.
[0284] In this manner, even when the elastomer web is made from
nonwoven fabric, the elongation (including heat treatment for
eliminating elongation stress) and the bonding to the nonwoven
fabric made from nonelastic fibers can be performed using the
aforementioned various apparatuses appropriately selected and the
aforementioned methods in accordance with the aligned direction of
the fibers.
[0285] When the aligned direction of the fibers in the nonwoven
fabric made from nonelastic fibers is equal to the aligned
direction of the elastomer fibers, overlaying means referred to as
an cross overlaying machine can be used to bond them. In the cross
overlaying machine, as shown in FIG. 31, nonwoven fabric 581 made
from elastomer is supplied in a direction perpendicular to the
carrying direction of nonwoven fabric 571 made from nonelastic
fibers. They are bonded with a heat pressing apparatus, not shown,
thereby obtaining a composite sheet having the nonelastic fibers
and the elastomer fibers arligned in perpendicular directions. The
composite sheet obtained with this method has a width equal to the
width of the nonwoven fabric. Therefore, when nonwoven fabric 581.
made from elastomer fibers is supplied, it is continuously overlaid
on nonwoven fabric 571 made from nonelastic fibers in a state where
it is cut in accordance with the width of nonwoven fabric 571 such
that an overlapping portion with previously supplied nonwoven
fabric 581a is minimized.
[0286] The elastomer web may be in the form of a net, knit or weave
formed from yarns of a thermoplastic elastomer, in addition to the
aforementioned film having openings or the nonwoven fabric.
[0287] (Seventh Embodiment)
[0288] While the aforementioned fourth to sixth embodiments provide
an example in which the nonelastic fibers and the elastomer web are
bonded to obtain the composite sheet having elasticity either in
the longitudinal direction or in the transverse direction, the
elastomer web used herein can be applied to a elastic web which can
be elongated in at least two directions.
[0289] In a seventh embodiment, description will be made for a
elastic web which can be elongated in at least two directions.
Elastic webs of this type can be both single webs and laminated
webs in terms of the structure.
[0290] (A) Single Web
[0291] FIGS. 32a to 32e show various examples of a material web
before elongation which is used for manufacturing the elastic web
having elasticity in two or more directions.
[0292] An example shown in FIG. 32a is film 610 made from
thermoplastic elastomer having a plurality of circular punched
holes 610a formed therein. An example shown in FIG. 32b is film 611
made from thermoplastic elastomer having a plurality of triangular
punched holes 611a formed therein. An example shown in FIG. 32c is
material web 612 in a nonwoven fabric-like pattern made from
filaments of a thermoplastic elastomer. An example shown in FIG.
32d is material web 613 in net shape with a rectangular-shaped mesh
made from thermoplastic elastomer. An example shown in FIG. 32e is
material web 614 in net shape with a rhombus-shaped mesh made from
thermoplastic elastomer.
[0293] Films 610, 611 and material webs 612, 613 and 614 shown in
FIGS. 32a to 32e are elongated in biaxial or longitudinal and
transverse directions or multi-axis direction and then, in that
state, subjected to heat treatment to eliminate the contractile
force, thereby obtaining elastic webs.
[0294] Next, description will be made for an example of an
apparatus used in elongating a material web in biaxial or
longitudinal and transverse directions and performing heat
treatment using a tentering stretching apparatus used for biaxial
stretching of films.
[0295] FIG. 33 shows a schematic plan view of an example of an
apparatus for elongating a material web in biaxial directions and
performing heat treatment. As shown in FIG. 33, the apparatus
includes two rails 341 disposed with space the transverse
direction. Each of rails 341 has a track long in the moving
direction of film 615. A plurality of grips 342 are attached to
each of rails 341 via a pantograph mechanism provided over the
entire track. Film 615 supplied between two rails 341 is held at
both side edges by grips 342 and moved in the direction shown by
arrows in FIG. 33 by means of the pantograph mechanism rounding
rails 341.
[0296] The interval between respective rails 341 is gradually
increased toward the downstream in the moving direction of film
615, and then substantially parallel. Film 615 is elongated
transversely in a transverse elongation zone in which the interval
between rails 341 is gradually increased, and is heated in a heat
treatment zone after that at a temperature equal to or higher than
the flow beginning temperature of the thermoplastic elastomer to
eliminate the contractile force. In FIG. 33, a heat source provided
in the heat treatment zone is not shown, but typically, hot wind,
an infrared heater or the like is used as a heat source.
[0297] The pantograph mechanism is operated in the aforementioned
transverse elongation zone such that the interval between adjacent
grips 342 is gradually increased as grips 342 move associated with
the working of the pantograph mechanism. This causes film 615 to be
elongated longitudinally simultaneously with the transverse
elongation.
[0298] The tentering stretching apparatus is advantageous in that
it can freely control the temperature in the transverse elongation
zone and the heat treatment zone and it can ensure a long time for
the heat treatment.
[0299] While grips 342 hold the both side edges of film 615 in the
apparatus shown in FIG. 33, the present invention is not limited
thereto, and the film can be held by putting pins into the film or
by another holding means. FIG. 33 shows the apparatus having the
pantograph mechanism which can change the interval between grips
342. However, if the apparatus is configured such that pantograph
mechanism is not used and grips 342 simply moves along the tracks
of rails 341, the film can be elongated only in the transverse
direction.
[0300] The apparatus is also advantageous in that the biaxial
elongation can produce a thinner and more flexible web, and also
produce a large-width web from a small-width web.
[0301] While description has been made for the example of tentering
scheme as means for biaxially elongating the film, the biaxial
elongation of the film is not limited to the tentering apparatus,
and biaxial elongation means using a pulley stretching apparatus
may be used as disclosed in Japanese Patent No.60408/89, Japanese
Patent Publication No.10851/92, Japanese Patent Publication
No.72455/91. Stretching means such as tubular biaxial stretching or
multi-axis stretching can be used as means for obtaining a elastic
web having elasticity in at least two directions in the present
invention.
[0302] (B) Laminated Web
[0303] Referring to FIG. 34, there is shown a elastic web having
elasticity in at least two directions obtained by overlaying a
plurality of webs with different elasticity directions.
[0304] Elastic web 620 shown in FIG. 34 is formed by bonding
longitudinally elongated film 621 to transversely elongated film
622. Longitudinally elongated film 621 has a longitudinally long
opening pattern similar to that shown in FIG. 25b formed by
elongating longitudinally and subjecting to heat treatment.
Transversely elongated film 622 has a transversely long opening
pattern similar to that shown in FIG. 18b formed by elongating
transversely and subjecting to heat treatment. Since longitudinally
elongated film 621 and transversely elongated film 622 are made
from thermoplastic elastomer, both of them are easily bonded only
by heating at least one of longitudinally elongated film 621 and
transversely elongated film 622. Therefore, a laminated web can be
simply obtained at low cost without using an adhesive or the
like.
[0305] While FIG. 34 illustrates the films used as webs for
description, nonwoven fabrics may be used as webs in addition to
the films as shown in the sixth embodiment.
[0306] While the nonwoven fabrics made from thermoplastic elastomer
are typically manufactured using a spun-bonding method or melt blow
method which is a typical spinning method of nonwoven fabrics, the
present invention is not limited thereto, and long fiber nonwoven
fabrics or short fiber nonwoven fabrics are applicable. Above all,
the manufacture is preferably performed using spinning methods and
stretching methods disclosed in Japanese Patent Publication
No.6126/95, Patent Publication No.2612203, Japanese Patent
Laid-open No.204767/98 which are earlier inventions by the present
inventors. The nonwoven fabrics manufactured by these methods have
air permeability and moisture permeability. The elongation and heat
treatment of the nonwoven fabric can be performed as the films.
[0307] For overlaying the webs, the apparatus shown in FIG. 13 can
be used when the webs have elongation directions different from one
another, while the cross overlaying machine as described using FIG.
31 can be employed if the webs having the elasticity in the same
direction are perpendicularly laminated to manufacture a laminated
web having elasticity in both longitudinal and transverse
directions. When the cross overlaying machine is used, particularly
preferable machines are those disclosed in Japanese Patent
Publication No.38783/78, Japanese Patent Publication No.40185/75,
and Japanese Patent Publication No.54582/82 which are earlier
inventions by the present inventors.
[0308] In bonding nonwoven fabrics, ultrasonic bonding, high
frequency bonding, physical bonding methods such as needle punch,
water jet or the like can be used in addition to the aforementioned
methods.
[0309] In the aforementioned bi-axially elongated web or laminated
web, the resulting product can be a web having elasticity not only
in the longitudinal direction and transverse direction but also in
directions at 45 degrees or other directions.
[0310] (Eighth Embodiment)
[0311] Referring to FIG. 35, there is shown composite sheet 710
according to an eighth embodiment of the present invention in
which, over one surface of nonwoven fabric 711 having nonelastic
fibers 711a aligned and stretched substantially longitudinally,
rubber elastic material 712 is provided in a stripe pattern in a
direction perpendicular to the aligned direction of fibers 711a.
Rubber elastic material 712 is arranged at intervals which serve as
air holes.
[0312] Since the configuration and characteristics of nonwoven
fabric 711 used for this composite sheet 710 are similar to those
described in the first embodiment, detailed description thereof is
omitted.
[0313] Such nonwoven fabric 711 is provided with rubber elastic
material 712 arranged at intervals in a direction perpendicular to
the aligned direction of fibers 711a, thereby obtaining composite
sheet 710 which is elastic transversely but is hardly elastic
longitudinally with favorable dimensional stability.
[0314] Additionally, as described above, the patterning of rubber
elastic material 712 long in the direction perpendicular to the
aligned direction of the fibers enhances the utilization efficiency
of the rubber elastic material material in the elasticity direction
of composite sheet 710, i.e. the transverse direction, making it
possible to ensure effective elasticity with a small amount of
rubber elastic material. Only a small amount of the rubber elastic
material required means not only a reduction in cost of the rubber
elastic material but also a corresponding reduction in weight of
composite sheet 710 and thus the range of uses is increased.
[0315] As rubber elastic material 712, a rubber elastic material
material having elasticity such as an elastomer of polyolefin base,
synthetic rubber, polyester base, polyamide base, polyurethane
base, or natural rubber is used. Of these materials, synthetic
rubber base or polyurethane base materials in which styrene and
olefin base monomers are copolymerized are preferable as rubber
elastic material material 712 used in the present invention due to
a high factor elasticity and a small stress at expanding.
Particularly, a synthetic rubber of SEBS is most preferable.
[0316] Next, a method of manufacturing the aforementioned composite
sheet 710 will be described using an example where a thermoplastic
elastomer is used as rubber elastic material material 712 with
reference to a flow chart in FIG. 36.
[0317] First, an appropriate spinning apparatus is used to form a
web having fibers 711a aligned substantially longitudinally, and
the web is stretched longitudinally, i.e. the aligned direction of
fibers 711a to manufacture nonwoven fabric 711 (step 1201).
[0318] Next, rubber elastic material material powder or a liquid
including the rubber elastic material material is applied on
nonwoven fabric 711 in a pattern shown in FIG. 35 (step 1202), and
nonwoven fabric 711 with the rubber elastic material material being
patterned thereon is heated at a temperature equal to or higher
than the flow beginning temperature of the rubber elastic material
material (step 1203).
[0319] When the thermoplastic elastomer is used as the rubber
elastic material material, the thermoplastic elastomer is
preferably used in the form of powder in the patterning on nonwoven
fabric 711. The thermoplastic elastomer powder can be directly
obtained in the process of the polymerization of the elastomer and
can be used as it is in that state in many cases. The manufacture
cost is thus lower, and in rubber elastic material material having
unfavorably formability, it is significantly advantageous to allow
the manufacture of a product directly from the powder.
[0320] Finally, nonwoven fabric 711 with the rubber elastic
material material being patterned thereon is pressed in a heated
state at a temperature equal to or higher than the flow beginning
temperature (step 1204) to bring the rubber elastic material
material into close contact with nonwoven fabric 711, thereby
obtaining composite sheet 710. When the rubber elastic material
material in a powder state is used, the grains of the powder are
mutually integrated at this point.
[0321] The aforementioned respective steps will be hereinafter
described in detail.
[0322] (8-a) Nonwoven Fabric Manufacturing Step
[0323] Since nonwoven fabric 711 having fibers 711a aligned and
stretched longitudinally can be manufactured similarly to that in
the aforementioned first embodiment, detailed description thereof
is omitted.
[0324] (8-b) Rubber Elastic Material Patterning Step
[0325] (8-c) Heating Step
[0326] (8-d) Pressing Step
[0327] These three steps are performed in series while nonwoven
fabric 711 obtained as described above is carried. These steps will
be described sequentially with reference to an apparatus in FIG.
37.
[0328] The apparatus shown in FIG. 37 manufactures the composite
sheet of the nonwoven fabric and the rubber elastic material by
using thermoplastic elastomer powder 712 as a rubber elastic
material material, continuously moving nonwoven fabric 711 at the
same time applying thermoplastic elastomer powder 712a to nonwoven
fabric 711 in a predetermined pattern, and performing heating and
pressing.
[0329] In FIG. 37, liquid 409 for patterning is contained in pot
401, and pot roller 402 is provided such that a portion of the
peripheral surface thereof is soaked in liquid 409 for patterning.
Pot roller 402 is in contact with transfer roller 403 provided on
its peripheral surface with projections 403a corresponding to a
pattern of the rubber elastic material to be provided on nonwoven
fabric 711. The peripheral surface of transfer roller 403 is also
in contact with carried nonwoven fabric 711. Liquid 409 for
patterning in pot 401 is attached via pot roller 402 to projections
403a of transfer roller 403 which comes into contact with nonwoven
fabric 711, thereby applying liquid 409 for patterning to the
surface of nonwoven fabric 711 in a pattern corresponding to
projections 403a of transfer roller 403.
[0330] Liquid 409 for patterning is provided for facilitating the
selective attachment of thermoplastic elastomer powder 712a onto
the surface of nonwoven fabric 711, as later described. As liquid
409 for patterning, water containing a surfactant, or a liquid
containing an adhesive, specifically a rubber emulsion adhesive, a
thickener or the like is used.
[0331] Hopper 404 for storing thermoplastic elastomer powder 712a
is provided on the downstream side from transfer roller 403 in the
moving direction of nonwoven fabric 711. Hopper 404 is provided for
putting powder. 712a on nonwoven fabric 711 which has liquid 409
for patterning applied thereon. Hopper 404 is provided on its
bottom end with a nozzle having a width equal to the width of
nonwoven fabric 711 such that powder 712a within hopper 404 is
thoroughly put on the upper surface of nonwoven fabric 711.
[0332] Nonwoven fabric 711 having powder 712a put thereon is then
turned by reversal roller 405 by 180 degrees and moved upside down.
At this point, powder 712a in the portions on which liquid 409 for
patterning is applied is still attached to nonwoven fabric 711 with
the surface tension or adhesion of the liquid. On the other hand,
powder 712a in the portions on which no liquid 409 for patterning
is applied falls by gravity and is held in powder receiver 406
disposed below reversal roller 405. As a result, nonwoven fabric
711 has powder 712a attached only in the portions on which liquid
409 for patterning is applied.
[0333] The nonwoven fabric is turned to drop unnecessary powder
712a in this example. However, if powder 712a is put on the entire
upper surface of nonwoven fabric 711 and then air is blown to
nonwoven fabric 711, powder 712a can be removed in the portions on
which no liquid 409 for patterning is applied while a surface of
nonwoven fabric 711 bonding to rubber elastic material 712 (FIG.
35) still faces upward.
[0334] Nonwoven fabric 711 to which thermoplastic elastomer 712a is
selectively attached in a predetermined pattern as described above
is subjected to heat treatment through heating furnace 407 having
infrared heaters 407a. Powder 712a is heated at a temperature equal
to or higher than the flow beginning temperature in this
section.
[0335] Nonwoven fabric 711 after passing through heating furnace
407 is subjected to pressing by nip rolls 408a, 408b in a state
where it is heated at the flow beginning temperature of powder 712a
or higher. This integrates the grains of the powder and enhances
the contact of the thermoplastic elastomer with nonwoven fabric
711.
[0336] As described above, the bonding of rubber elastic material
712 to nonwoven fabric 711 is performed in a series of steps by
directly patterning the rubber elastic material material on
nonwoven fabric 711 and performing heat treatment thereof, which
eliminates the need for the step of individually manufacturing
rubber elastic material 712 of unfavorable workability and the step
of bonding nonwoven fabric 711 to rubber elastic material 712. As a
result, composite sheet 710 can be conveniently and efficiently
manufactured.
[0337] The embodiment illustrates the method in which powder 712a
is put on the entire upper surface of nonwoven fabric 711 and then
powder 712a is removed in the portions requiring no powder as a
method of selectively attaching thermoplastic elastomer powder 712a
to nonwoven fabric 711 having liquid 409 for patterning applied
thereto in a predetermined pattern. Another example will be
described in the following.
[0338] FIG. 38 is a schematic diagram showing another example of an
apparatus for manufacturing the composite sheet according to the
present invention. In FIG. 38, the same components as those in FIG.
37 are designated with the same reference numerals as those in FIG.
37, and detailed description thereof is omitted.
[0339] In the apparatus shown in FIG. 38, nonwoven fabric 711 is
carried with its surface to which rubber elastic material 712 (FIG.
35) is to be bonded facing downward. Powder flow bath 411 for
storing thermoplastic elastomer powder 712a is disposed below
nonwoven fabric 711 between transfer roller 403 and heating furnace
407 in the carrying path of nonwoven fabric 711. Powder flow bath
411 comprises a container having an open top surface in which fans
411a for blowing air are disposed. The operation of fans 411a
generates air flow in powder flow bath 411 to cause powder 712a in
powder flow bath 411 to be blown toward nonwoven fabric 711.
[0340] As nonwoven fabric 711 to which liquid 409 for patterning is
applied in a predetermined pattern passes over powder flow bath
411, powder 712a comes into contact with nonwoven fabric 711. At
this point, powder 712a in contact with the portions to which
liquid 409 for patterning is applied remains attached to nonwoven
fabric 711 with the surface tension or adhesion of the liquid. On
the other hand, powder 712a in contact with the portions to which
no liquid 409 for patterning is applied falls without attachment to
nonwoven fabric 711. As a result, powder 712 is attached only to
the portions of nonwoven fabric 711 to which liquid 409 for
patterning is applied.
[0341] Thereafter, nonwoven fabric 711 having thermoplastic
elastomer 712a selectively attached in a predetermined pattern is
subjected to heat treatment in heating furnace 407 and to pressing
with nip rollers 408a, 408b, similarly to the apparatus shown in
FIG. 37.
[0342] While the embodiment illustrates rubber elastic material 712
provided on nonwoven fabric 711 in the pattern shown in FIG. 35,
the pattern of rubber elastic material 712 can be arbitrarily
changed by modifying the pattern of projections 403a provided on
transfer roller 403 of the apparatus shown in FIG. 37 or FIG.
38.
[0343] For example, in composite sheet 715 shown in FIG. 39, rubber
elastic material 717 is provided in an elongated island pattern in
a direction perpendicular to the aligned direction of fibers 716a
of nonwoven fabric 716. Rubber elastic material 717 provided in
such an island pattern also achieves elasticity similar to that of
composite sheet 710 shown in FIG. 35.
[0344] (Ninth Embodiment)
[0345] Referring to FIG. 40, there is shown composite sheet 720
according to a ninth embodiment of the present invention. In
composite sheet 720 shown in FIG. 40, rubber elastic material 722
is provided in a pattern with a number of openings 722a long in the
longitudinal direction over one surface of nonwoven fabric 721
having fibers 721a aligned and stretched substantially
transversely.
[0346] Composite sheet 720 of the embodiment has nonwoven fabric
721 and rubber elastic material 722 opposite to those in the eighth
embodiment in terms of longitudinal and transverse directions.
Therefore, its characteristics are also opposite to those of the
composite sheet described in the eighth embodiment in terms of
longitudinal and transverse directions. Specifically, composite
sheet 720 of the embodiment is elastic longitudinally but is hardly
expanded transversely with favorable dimensional stability. Other
characteristics such as air permeability (moisture permeability),
high utilization efficiency of the elastomer and the like are
similar to those in the eighth embodiment. The same materials
constituting nonwoven fabric 711 and elastomers as those in the
eighth embodiment can be used.
[0347] Composite sheet 720 in the embodiment is basically
manufactured through the respective steps shown in FIG. 36
similarly to the composite sheet in the eight embodiment. However,
since nonwoven fabric 721 has fibers 721a aligned substantially
transversely, steps of manufacturing nonwoven fabric 721 are
different from those in the eight embodiment.
[0348] Methods for manufacturing nonwoven fabric 721 having fibers
721a aligned transversely include those, for example, disclosed in
Japanese Patent Publication No.36948/91, Japanese Patent Laid-open
No.6126/95, Japanese Patent No.2612203, Domestic Republication of
PCT International Publication for Patent Application WO9617121,
Japanese Patent Laid-open No.204764/98, Japanese Patent Laid-open
No.222759/99, or the like. Nonwoven fabric 721, even when
manufactured with such other manufacturing methods, can be used as
long as elongation in one direction is 100% or higher.
[0349] Next, the nonwoven fabric having fibers 721a aligned
transversely is stretched transversely. The transverse stretching
of the nonwoven fabric can be performed using, for example, the
apparatus shown in FIG. 11.
[0350] After nonwoven fabric 721 having fibers 721a aligned and
stretched transversely is manufactured, composite sheet 720 is
manufactured using the apparatus shown in FIG. 37, the apparatus
shown in FIG. 38 or the like. Specifically, thermoplastic elastomer
powder is attached to nonwoven fabric 721 in the pattern of rubber
elastic material 721 shown in FIG. 40, and nonwoven fabric 721 is
heated and then pressed, thereby obtaining composite sheet 720.
[0351] While the eight and ninth embodiments illustrate the
composite sheet obtained by applying the rubber elastic material
onto the nonwoven fabric in a predetermined pattern, the method of
applying the rubber elastic material onto the nonwoven fabric is
not limited to those shown in the aforementioned embodiments, and
various methods can be employed. In the following, other example of
the method of applying the rubber elastic material will be
described.
[0352] The methods of patterning the rubber elastic material on the
nonwoven fabric include, in addition to separate attachment of the
liquid for patterning and the thermoplastic elastomer powder as in
the described example, previously dispersing thermoplastic
elastomer powder into a dispersant, an adhesive, specifically
rubber emulsion adhesive, a rubber latex, a thickener or the like
and applying the powder dispersed liquid in a predetermined pattern
for direct patterning to the nonwoven fabric. The methods of
applying the powder dispersed liquid at this point include
application utilizing known printing dyeing means by using the
powder dispersed liquid as a dye. Alternatively, typical powder
coating schemes, for example electrostatic coating can be used
without using the liquid for patterning.
[0353] Additionally, the rubber elastic material in the patterning
may be in liquid form containing the rubber elastic material in
addition to the thermoplastic elastomer powder. In this case, for
example, the liquid containing the rubber elastic material is used
as printing ink and applied to the nonwoven fabric in a
predetermined pattern with a known printing machine, or the liquid
containing the rubber elastic material is used as a dye and applied
to the nonwoven fabric in a predetermined pattern with a known
printing dyeing machine.
[0354] The liquid containing the rubber elastic material include a
synthetic rubber base emulsion, a natural rubber latex, a solution
in which rubber is dissolved in a solvent, or the like. In any
case, a cross-linking agent is added, and as required, an additive
such as another adhesion inhibitor is added to them before use.
After the application of the liquid containing the rubber elastic
material to the nonwoven fabric, drying or heat treatment is
performed for removing the solvent in the solution in water within
the emulsion and for promoting the reaction of the cross-linking
agent, thereby bringing the rubber elastic material into contact
with the nonwoven fabric. Pressing or the like is performed as
required in a heated state to enhance the contact with the nonwoven
fabric.
[0355] The composite sheet according to the present invention has
elasticity in one direction as described above, and is suitable
specifically for elastic portions such as base materials for tie
tapes, elastic portions of hygiene products, interlinings for
clothes, base materials for elastic adhesive bandages, elastic
support bandages, supporters for medical use, elastic portions of
diapers, poultice base materials, elastic members for clothes in
collars, ends of sleeves or waist portions, elastic portions in
operating gowns or caps for medical use, artificial leathers, base
cloths for gloves, suspenders, belts, garters, base cloths for
masks, arm covers, base cloths for elastic clothes, corsets.
[0356] According to the present invention, since a small amount of
a rubber elastic material can most efficiently exert elasticity and
a composite sheet can be obtained with a convenient and efficient
forming method, the composite sheet of the present invention is
favorably mass-produced.
[0357] The nonwoven fabric used in the present invention is
stretched in one direction having filaments aligned in one
direction with the best efficiency such that it is suited for
obtaining large elongation in a direction perpendicular to the
aligned direction of the filaments, and the elongation
characteristic is not impaired even with a small fiber amount per
square meter of the nonwoven fabric. Therefore, the amount of the
nonwoven fabric can be reduced, and also in terms of that
reduction, the sheet can be provided with low cost.
[0358] On the other hand, the elastic web according to the present
invention has elasticity in one direction or at least two
directions by itself, but it is bonded to another elastic material,
for example to a nonwoven fabric or the like to be preferably used
for the aforementioned applications.
[0359] As described above, the present invention has been described
with the typical embodiments thereof used as examples. In the
following, specific embodiments and comparative examples of the
present invention will be given.
Examples of Composite Sheet
Example 1-1
[0360] First, a longitudinally stretched nonwoven fabric was
manufactured as follows.
[0361] A PET (Polyethylene Terephthalate) molten resin at [.eta.]
0.63 dl/g was spun from melt blow die 1 shown in FIG. 2 at a nozzle
diameter of 0.3 mm, die temperature of 300.degree. C., hot wind
temperature of 350.degree. C. At this point, heated air at high
pressure was ejected from one air chamber 5a at 4
liter/minute/nozzle, and from the other air chamber 5b at 5
liter/minute/nozzle. Inclination angle .alpha. of nozzle 3 was 12
degrees. Spray nozzles 8a, 8b sprayed atomized water to a position
250 mm away from nozzle 3 to set angle .beta. at 45 degrees.
[0362] Conveyor 7 comprised a screen with 2 mm mesh traveling at 10
m/minute, and was disposed to form angle .gamma. of 25 degrees with
respect to the horizontal plane. Negative pressure sucking nozzle
10 had the same width of that of web 9 and was disposed to have a
gap of 8 mm between itself and the back side of conveyor 7 at the
arrival point of the filaments.
[0363] Web 9 on conveyor 7 was preheated to 85.degree. C. by a
cylinder with a diameter of 500 mm and then nipped onto stretching
cylinder 11 by retaining rubber roll 13. The stretching point was
heated in the width direction by infrared line heater 32 shown in
FIG. 5b to longitudinally stretch the web by a factor of 2.5.
[0364] Next, the stretching apparatus shown in FIG. 3 was used to
perform stretching. However, in this example, stretching roll 51
was used as a heat treatment roll and heat treatment roll 54 was
used as a cooling cylinder. Specifically, the temperatures of
preheat roll 43 and stretching roll 45 were set at 85.degree. C. to
stretch the web by a factor of two between P and Q. A cover was put
over the section between stretching roll 48 at 120.degree. C. and
stretching roll (51) at 165.degree. C. to form a steam room within
the cover in which the web was further stretched by a factor of
1.2. The web was shrunk 3% between stretching roll (51) and cooling
cylinder (54).
[0365] The resulting nonwoven fabric had a fiber amount per square
meter of 35 g/m.sup.2, elongation of 10% in the longitudinal
direction, a strength of 2.3 g/d in the longitudinal direction,
elongation of 200% in the transverse direction, a strength of 0.3
g/d in the transverse direction. The elongation and strength of the
nonwoven fabric were values at break.
[0366] Next, the longitudinally stretched nonwoven fabric obtained
as described above was introduced to guide cylinder 83 of the
apparatus shown in FIG. 4, at the same time the elastomer was
sprayed from spray head 87, thereby bonding the elastomer to the
nonwoven fabric to manufacture a composite sheet. As the elastomer,
SEBS, KratonG (product name: made by Shell Chemical Co.) made by
Shell Japan Co, Ltd. was used. The spinning head had an outer
diameter of 200 mm and two nozzles. The spinning head was rotated
at 1500 r.p.m. and the elastomer was spun to the nonwoven fabric.
The guide cylinder had an inner diameter of 500 mm. The strand of
the elastomer spun to the nonwoven fabric had a diameter of 0.5
mm.
[0367] The resulting composite sheet was characterized by
elongation of 10% in the longitudinal direction and elongation of
300% in the transverse direction. The elongation of the composite
sheet represents the maximum elastic elongation in the transverse
direction, and represents elongation at break in the longitudinal
direction. When elongation of a composite sheet is presented in the
following examples, similarly, the elongation in a direction with a
larger elongation is the maximum elastic elongation, while the
elongation in a direction with a smaller elongation is the
elongation at break.
Example 1-2
[0368] An elastomer web having orientation in the transverse
direction manufactured using the apparatus shown in FIG. 9a to FIG.
9c was bonded onto a longitudinally stretched nonwoven fabric
manufactured similarly to the example 1-1 using the apparatus shown
in FIG. 13 to manufacture a composite sheet. The elastomer similar
to that in the example 1-1 was used.
[0369] The resulting composite sheet was characterized by
elongation of 10% in the longitudinal direction and elongation of
200% in the transverse direction.
Example 1-3
[0370] A spun-bonded nonwoven fabric (amount per square meter of 80
g/m.sup.2) available on the market was stretched by a factor of 2.5
in horizontally direction at hot air temperature of 120.degree. C.,
using stretching apparatus shown in FIG. 11, whereby a horizontally
stretched nonwoven fabric of which amount per square meter of 38
g/m.sup.2 was manufactured. The resulting nonwoven fabric had a
strength of 1.7 g/tex in the vertical direction, elongation of 108%
in the vertical direction, a strength of 13.5 g/tex in the
horizontal direction, elongation of 22% in the horizontal
direction.
[0371] Next, as shown in FIGS. 41a and 41b, while feeding the
horizontally stretched nonwoven fabric 801, thermoplastic elastomer
803 was pushed out from a large number of filament dies 802
arranged 5 mm pitch in width direction. The strands of the vertical
direction were formed on the nonwoven fabric 801 by the
thermoplastic elastomer 803. SEBS (styrene--ethylene
butylene--styrene) base polymer (Kraton G1657 of Shell Japan Co.
Ltd.) was used as the thermoplastic elastomer 803. The strands of
the elastomer 803 and the nonwoven fabric 801 were integrated by
pinching before the elastomer 803 solidifies, and were cooled with
nip rolls 804 and a composite sheet which shows large elasticity in
the vertical direction was obtained. The fineness of the elastomer
was 500 tex.
[0372] The elongation of the composite sheet was 270% in the
vertical direction, the strands ware not peeled off from the
nonwoven fabric 801 even if the composite sheet was elongated 200%
in vertical direction 5 times. Moreover, the residual strain of the
composite sheet was 18%.
Example 1-4
[0373] First, a polyethylene terephthalate resin (IV value 0.62)
was used to provide a nonwoven fabric stretched longitudinally by a
factor of 5.2 (basis weight 15 g/m.sup.2) with the scheme described
in Japanese Patent Application No.10-34242. The nonwoven fabric had
a strength of 1.6 g/d in the longitudinal direction, elongation of
14% in the longitudinal direction, and a strength of 0.04 g/d in
the transverse direction, elongation of 185% in the transverse
direction. The strength and elongation of the nonwoven fabric were
measured in compliance with JIS L1906 (Test methods for non-woven
fabric made of filament yarn), and the strength was represented
with conversion to denier so as to adapt to various basis
weights.
[0374] Next, the longitudinally stretched nonwoven fabric was
supplied to the apparatus shown in FIG. 37, and liquid 409 for
patterning was applied to the nonwoven fabric with transfer roller
403. The pattern of liquid 409 for patterning to be attached to the
nonwoven fabric was that of the rubber elastic material shown in
FIG. 39. Liquid 409 for patterning was 0.4% aqueous solution of
polyethylene oxide (PEO-15 made by Sumitomo Seika Chemicals Co,
Ltd.) which has increased viscosity of water to provide adhesion.
After the application of liquid 409 for patterning, thermoplastic
elastomer powder 712a was dropped from hopper 404 on the nonwoven
fabric, and then, the nonwoven fabric was turned by reversal roller
405 to leave powder 712a on the nonwoven fabric in the pattern
shown in FIG. 39. As powder 712a, the copolymerized polymer of
styrene and ethylene butylene (Kraton G1652 of Shell Japan Co,
Ltd.) was used. The nonwoven fabric having powder 712a attached
only to the portions to which liquid 409 for patterning was applied
was heated by heating furnace 407 at 230.degree. C. and pressed by
nip rollers 408a, 408b. This flattened powder 712a and enhanced the
adhering of the elastomer and the nonwoven fabric, thereby
obtaining a composite sheet.
[0375] The resulting composite sheet had elongation of 16% in the
longitudinal direction and 420% in the transverse direction. The
repeated elongation of 200% of the composite sheet in the
transverse direction on ten times showed a stress reduction rate of
21% at elongation of 200% and residual strain of 12%, thar results
indicated that the composite sheet was practicable as a
transversely elastic sheet.
Example 1-5
[0376] A polypropylene resin (MFR520) was used to provide a
nonwoven fabric (basis weight 20 g/m.sup.2) obtained by
transversely stretching a spun nonwoven fabric with a transverse
arrangement by a factor of 5.8 with the scheme described in
Japanese Patent Publication No.6126/95. The nonwoven fabric had a
strength of 0.05 g/d in the longitudinal direction, elongation of
220% in the longitudinal direction, a strength of 2.1 g/d in the
transverse direction, elongation of 18% in the transverse
direction.
[0377] Next, thermoplastic elastomer powder was attached to the
transversely stretched nonwoven fabric in the pattern of the rubber
elastic material shown in FIG. 40 with flexography using a
cross-linking agent mixed in a natural rubber latex to obtain a
composite sheet. The natural rubber latex had solid matters of 60%
and contains ammonia of 0.2%. The cross-linking agent containing
zinc oxide, sulfur and reaction accelerator was used by mixing the
latex solid matters and the cross-linking agent solid matters in
the proportion of 100:5. The cross-linking was formed for three
minutes at 110.degree. C.
[0378] The resulting composite sheet had elongation of 540% in the
longitudinal direction and 21% in the transverse direction. The
repeated elongation of 200% of the composite sheet in the
longitudinal direction on ten times showed a stress reduction rate
of 26% at elongation of 200% and residual strain of 15%, that
results indicated that the composite sheet was practicable as a
longitudinally elastic sheet.
Example 1-6
[0379] Raw material of a short fiber was put in the carding engine
to obtain the carded web which amounts 50 g/m.sup.2. The raw
material was mixture of polyethylene telephthalate short fibers
(0.25 tex, the length of 50 mm) and polyester base low melting
point short fiber (MELTY 2080 of UNITIKA, LTD.). The ratio was 75%
to 25%. This web was embossed at 180.degree. C., and the nonwoven
fabric made of longitudinally aligned short fibers was obtained.
The resulting nonwoven fabric had a strength of 12.7 g/tex and
elongation of 28% in the vertical direction, a strength of 1.1
g/tex and elongation of 115% in the horizontal direction. The
strands (100 tex) of above mentioned SEBS base polymer was arranged
on the nonwoven fabric in 3 mm pitch at the horizontal direction
and pressed at 140.degree. C. by using the same cross overlaying
machine as it is described in Japanese Patent Publication
No.40185/75, Japanese Patent Publication No.38783/78, or Japanese
Patent Publication No.57222/91, thereby a composite sheet which
shows large strechability in the horizontal direction was
obtained.
[0380] The overlaying process of the nonwoven fabric and the
strands by the cross overlaying machine is explained with FIGS. 42a
and 42b. As shown in FIG. 42a, many strands 853 are wound on
bobbins 852 in creel stand 851. The strands 853 are pulled out by
nip rolls 855 through warping comb 854. The pulled strands 853 are
arranged at regular intervals on lattice 856. Strands 853 on the
lattice 856 are served as the group of strands 853' cut by cutter
857 in equivalent length to the width of the nonwoven fabric 861.
On the other hand, as shown in FIG. 42b, an adhesive 862 is applied
on the nonwoven fabric 861 by a kiss roll 863. The nonwoven fabric
861 on which applied the adhesive 862 is pressed against the group
of strands 853' on the lattice 856 with belt 864 by belt push
members 865. As a result, the group of strands 853' are transferred
to the nonwoven fabric 861. Thereby, the group of strands 853' are
arranged in the horizontal direction on the nonwoven fabric 861.
The group of strands 853' and the nonwoven fabric 861 are unified
by pinching with nip roll 867 after heated with heating cylinder
866, thereby the composite sheet which shows large strechability in
horizontal direction was obtained.
[0381] Although the arrangement of the strands in horizontal
direction is made by using the cross overlaying machine in this
example, it may be made by weft inserting the strands of
thermoplastic elastmer with weaving machine available on the
market.
Comparative Example 1-1
[0382] An elastomer nonwoven fabric (with elongation of 200% in
longitudinal and transverse directions) was integrated with a
nonwoven fabric (with elongation of 25% in the longitudinal
direction and elongation of 40% in the transverse direction)
manufactured by conventional MB manufacturing equipment, using a
calender roll. The resulting composite sheet was elongated 200%
respectively in longitudinal and transverse directions, but at the
same time the nonwoven fabric was broken at elongation of 25% in
the longitudinal direction and elongation of 40% in the transverse
direction, and the contact points were peeled.
Comparative Example 1-2
[0383] A nonwoven fabric (with elongation of 25% in the
longitudinal direction and elongation of 30% in the transverse
direction) manufactured by conventional SB manufacturing equipment
was bonded to an elastomer base material. In the resulting
composite sheet, the nonwoven fabric was broken and the contact
points were peeled when deformation exceeds the elongation of the
nonwoven fabric used.
Examples of Elastic Web
Example 2-1
[0384] Transversely Elongated Film
[0385] First, slits with a length of 5 mm and a pitch of 2.5 mm in
the transverse direction were formed in a film with a thickness of
200 .mu.L m made from SEBS base resin (product name "KratonG1657"
made by Shell Japan Co, Ltd.) in a staggered pattern as shown in
FIG. 18. Next, the film having the slits formed therein was
elongated transversely by a factor of 3.5 with the apparatus shown
in FIG. 11, subjected to heat treatment at 135.degree. C. to
eliminate the contractile force of the film, and flattened with a
heat pressing mechanism shown in FIG. 20, thereby obtaining a
elastic web. The resulting web had a thickness of 32 .mu.m with
repeated elasticity in the transverse direction.
Example 2-2
[0386] Longitudinally Elongated Nonwoven Fabric
[0387] A nonwoven fabric (product name "Espansione" made by Kanebo,
Ltd. with a basis weight of 50 g/m.sup.2) made from polyurethane
was stretched longitudinally by a factor of 3.8 with the apparatus
shown in FIG. 27, subjected to heat treatment at 138.degree. C. and
to heat pressing, thereby obtaining a elastic web. The resulting
web could resist repeated elongation of 200% in the longitudinal
direction.
Example 2-3
[0388] Biaxially Elongated Film
[0389] Punched holes with a diameter of 1 mm as shown in FIG. 32a
were formed in a film with a thickness of 300 .mu.m made from
thermoplastic elastomer (made by Kuraray Co, Ltd., product name
"SEPTON 2063") which is a styrene-isoprene base copolymer. Next,
the film was stretched longitudinally by a factor of 2 and
transversely by a factor of 2.5 with the tentering biaxial
stretching apparatus shown in FIG. 33 and subjected to shrinkage
heat treatment of 10% in the longitudinal direction and 15% in the
transverse direction at 145.degree. C., thereby obtaining a elastic
web. The resulting web could resist repeated elasticity of 300% not
only in longitudinal and transverse directions but also in all
directions including directions at 45 degrees.
[0390] While preferred embodiments of the present invention have
been described using specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
* * * * *